diff --git a/src/main/java/com/sajang/devracebackend/controller/RoomController.java b/src/main/java/com/sajang/devracebackend/controller/RoomController.java
index cbf058b..2d44bf8 100644
--- a/src/main/java/com/sajang/devracebackend/controller/RoomController.java
+++ b/src/main/java/com/sajang/devracebackend/controller/RoomController.java
@@ -2,10 +2,9 @@
 
 import com.sajang.devracebackend.config.RabbitConfig;
 import com.sajang.devracebackend.dto.problem.ProblemSaveRequestDto;
-import com.sajang.devracebackend.dto.room.RoomSaveResponseDto;
+import com.sajang.devracebackend.dto.room.RoomResponseDto;
 import com.sajang.devracebackend.dto.room.RoomWaitRequestDto;
 import com.sajang.devracebackend.dto.room.RoomWaitResponseDto;
-import com.sajang.devracebackend.dto.userroom.CodeRoomResponseDto;
 import com.sajang.devracebackend.dto.userroom.UserPassRequestDto;
 import com.sajang.devracebackend.dto.userroom.RoomCheckAccessResponseDto;
 import com.sajang.devracebackend.dto.room.RoomCheckStateResponseDto;
@@ -18,10 +17,6 @@
 import io.swagger.v3.oas.annotations.tags.Tag;
 import lombok.RequiredArgsConstructor;
 import org.springframework.amqp.rabbit.core.RabbitTemplate;
-import org.springframework.data.domain.Page;
-import org.springframework.data.domain.Pageable;
-import org.springframework.data.domain.Sort;
-import org.springframework.data.web.PageableDefault;
 import org.springframework.http.ResponseEntity;
 import org.springframework.messaging.handler.annotation.MessageMapping;
 import org.springframework.messaging.handler.annotation.Payload;
@@ -41,9 +36,16 @@ public class RoomController {
 
     @PostMapping("/rooms")
     @Operation(summary = "방생성 Page - 방 생성 [jwt O]")
-    public ResponseEntity<ResponseData<RoomSaveResponseDto>> createRoom(@RequestBody ProblemSaveRequestDto problemSaveRequestDto) throws IOException {
-        RoomSaveResponseDto roomSaveResponseDto = roomService.createRoom(problemSaveRequestDto);
-        return ResponseData.toResponseEntity(ResponseCode.CREATED_ROOM, roomSaveResponseDto);
+    public ResponseEntity<ResponseData<RoomResponseDto>> createRoom(@RequestBody ProblemSaveRequestDto problemSaveRequestDto) throws IOException {
+        RoomResponseDto roomResponseDto = roomService.createRoom(problemSaveRequestDto);
+        return ResponseData.toResponseEntity(ResponseCode.CREATED_ROOM, roomResponseDto);
+    }
+
+    @GetMapping("/rooms")
+    @Operation(summary = "초대링크 방 조회 [jwt O]", description = "URI : /rooms?link={방링크 string}")
+    public ResponseEntity<ResponseData<RoomResponseDto>> findRoomByLink(@RequestParam(value = "link", required = true) String link) {
+        RoomResponseDto roomResponseDto = roomService.findRoomByLink(link);
+        return ResponseData.toResponseEntity(ResponseCode.READ_ROOM, roomResponseDto);
     }
 
     @GetMapping("/rooms/{roomId}")
@@ -68,7 +70,7 @@ public ResponseEntity<ResponseData<RoomCheckStateResponseDto>> checkState(@PathV
     }
 
     @PostMapping("/rooms/{roomId}")  // 의미상 PUT보단 POST가 더 적합하다고 판단했음.
-    @Operation(summary = "문제풀이 Page - 문제풀이 실패 및 성공 [jwt O]", description = "isRetry==0 : 첫풀이 경우 / isRetry==1 : 재풀이 경우")
+    @Operation(summary = "문제풀이 Page - 문제풀이 성공 및 실패/퇴장 [jwt O]", description = "isRetry==0 : 첫풀이 경우 / isRetry==1 : 재풀이 경우")
     public ResponseEntity<ResponseData> passSolvingProblem(
             @PathVariable(value = "roomId") Long roomId,
             @RequestBody UserPassRequestDto userPassRequestDto) {
@@ -84,24 +86,6 @@ public ResponseEntity<ResponseData> userStopWaitRoom(@PathVariable(value = "room
         return ResponseData.toResponseEntity(ResponseCode.UPDATE_ROOM);
     }
 
-    @GetMapping("/rooms")
-    @Operation(summary = "내 코드방 목록 조회/정렬/검색 [jwt O]",
-            description = """
-                - 전체 정렬 URI : /rooms?page={페이지번호 int}
-                - 성공or실패 정렬 URI : /rooms?isPass={풀이성공여부 int}&page={페이지번호 int}
-                - 문제번호 검색 URI : /rooms?number={문제번호 int}&page={페이지번호 int}
-                - 초대링크 탐색 URI : /rooms?link={방링크 string}  \nsize, sort 필요X (기본값 : page=0 & size=9 & sort=createdTime,desc)
-                """)
-    public ResponseEntity<ResponseData<Page<CodeRoomResponseDto>>> findCodeRoom(
-            @RequestParam(value = "isPass", required = false) Integer isPass,
-            @RequestParam(value = "number", required = false) Integer number,
-            @RequestParam(value = "link", required = false) String link,
-            @PageableDefault(page=0, size=9, sort="createdTime", direction = Sort.Direction.DESC) Pageable pageable) {
-
-        Page<CodeRoomResponseDto> codeRoomResponseDtoPage = userRoomService.findCodeRoom(isPass, number, link, pageable);
-        return ResponseData.toResponseEntity(ResponseCode.READ_USERROOM, codeRoomResponseDtoPage);
-    }
-
     @MessageMapping("wait.enter")  // 웹소켓 메시지 처리 (백엔드로 '/pub/wait.enter'를 호출시 이 브로커에서 처리)
     public void userWaitRoom(@Payload RoomWaitRequestDto roomWaitRequestDto) {
         // '/exchange/wait.exchange/waitingroom.{roomId}' 구독되어있는 프론트엔드에게 메세지 전달.
diff --git a/src/main/java/com/sajang/devracebackend/controller/UserController.java b/src/main/java/com/sajang/devracebackend/controller/UserController.java
index 4a3398b..4942952 100644
--- a/src/main/java/com/sajang/devracebackend/controller/UserController.java
+++ b/src/main/java/com/sajang/devracebackend/controller/UserController.java
@@ -4,18 +4,21 @@
 import com.sajang.devracebackend.dto.user.UserResponseDto;
 import com.sajang.devracebackend.dto.user.UserSolvedResponseDto;
 import com.sajang.devracebackend.dto.user.UserUpdateRequestDto;
+import com.sajang.devracebackend.dto.userroom.CodeRoomResponseDto;
 import com.sajang.devracebackend.response.ResponseCode;
 import com.sajang.devracebackend.response.ResponseData;
+import com.sajang.devracebackend.service.UserRoomService;
 import com.sajang.devracebackend.service.UserService;
 import io.swagger.v3.oas.annotations.Operation;
 import io.swagger.v3.oas.annotations.tags.Tag;
 import lombok.RequiredArgsConstructor;
+import org.springframework.data.domain.Page;
+import org.springframework.data.domain.Pageable;
+import org.springframework.data.domain.Sort;
+import org.springframework.data.web.PageableDefault;
 import org.springframework.http.MediaType;
 import org.springframework.http.ResponseEntity;
-import org.springframework.web.bind.annotation.GetMapping;
-import org.springframework.web.bind.annotation.PutMapping;
-import org.springframework.web.bind.annotation.RequestPart;
-import org.springframework.web.bind.annotation.RestController;
+import org.springframework.web.bind.annotation.*;
 import org.springframework.web.multipart.MultipartFile;
 
 import java.io.IOException;
@@ -26,6 +29,7 @@
 public class UserController {
 
     private final UserService userService;
+    private final UserRoomService userRoomService;
 
 
     @GetMapping("/users")
@@ -50,17 +54,33 @@ public ResponseEntity<ResponseData> updateUserProfile(
         return ResponseData.toResponseEntity(ResponseCode.UPDATE_USER);
     }
 
-    @GetMapping("/users/solved-count")
-    @Operation(summary = "백준 solvedCount값 조회 [jwt O]")
-    public ResponseEntity<ResponseData<UserSolvedResponseDto>> checkUserSolvedCount() {
-        UserSolvedResponseDto userSolvedResponseDto = userService.checkUserSolvedCount();
-        return ResponseData.toResponseEntity(ResponseCode.READ_SOLVEDCOUNT, userSolvedResponseDto);
+    @GetMapping("/users/rooms")
+    @Operation(summary = "코드방 목록 조회/정렬/검색 [jwt O]",
+            description = """
+                - 전체 정렬 URI : /users/rooms?page={페이지번호 int}
+                - 성공or실패 정렬 URI : /users/rooms?isPass={풀이성공여부 int}&page={페이지번호 int}
+                - 문제번호 검색 URI : /users/rooms?number={문제번호 int}&page={페이지번호 int}  \nsize, sort 필요X (기본값 : size=9 & sort=createdTime,desc)
+                """)
+    public ResponseEntity<ResponseData<Page<CodeRoomResponseDto>>> findCodeRooms(
+            @RequestParam(value = "isPass", required = false) Integer isPass,
+            @RequestParam(value = "number", required = false) Integer number,
+            @PageableDefault(size=9, sort="createdTime", direction = Sort.Direction.DESC) Pageable pageable) {
+
+        Page<CodeRoomResponseDto> codeRoomResponseDtoPage = userRoomService.findCodeRooms(isPass, number, pageable);
+        return ResponseData.toResponseEntity(ResponseCode.READ_USERROOM, codeRoomResponseDtoPage);
     }
 
-    @GetMapping("/users/room-check")
+    @GetMapping("/users/rooms-check")
     @Operation(summary = "메인 Page - 참여중인 방 여부 검사 [jwt O]", description = "roomId == Long or null")
     public ResponseEntity<ResponseData<UserCheckRoomResponseDto>> checkCurrentRoom() {
         UserCheckRoomResponseDto userCheckRoomResponseDto = userService.checkCurrentRoom();
         return ResponseData.toResponseEntity(ResponseCode.READ_ROOM, userCheckRoomResponseDto);
     }
+
+    @GetMapping("/users/solved-count")
+    @Operation(summary = "백준 solvedCount값 조회 [jwt O]")
+    public ResponseEntity<ResponseData<UserSolvedResponseDto>> checkUserSolvedCount() {
+        UserSolvedResponseDto userSolvedResponseDto = userService.checkUserSolvedCount();
+        return ResponseData.toResponseEntity(ResponseCode.READ_SOLVEDCOUNT, userSolvedResponseDto);
+    }
 }
diff --git a/src/main/java/com/sajang/devracebackend/domain/Room.java b/src/main/java/com/sajang/devracebackend/domain/Room.java
index 5481cb0..11908f3 100644
--- a/src/main/java/com/sajang/devracebackend/domain/Room.java
+++ b/src/main/java/com/sajang/devracebackend/domain/Room.java
@@ -36,14 +36,14 @@ public class Room extends BaseEntity implements Serializable{
     @Column(name = "room_state")
     private RoomState roomState;
 
+    // Room 조회시 Room.problem N+1 문제 해결 ==> Eager 조회 : '@EntityGraph 적용 메소드 활용', Lazy 조회 : '기본 지연로딩 용도'
     @ManyToOne(fetch = FetchType.LAZY)  // Room-Problem 단방향매핑
     @JoinColumn(name = "problem_id")
     private Problem problem;
 
-    // 밑처럼 과도한 N+1 문제를 유발할 서비스 로직이 없을뿐더러 활용 빈도수도 낮기때문에, fetch join이나 @EntityGraph를 사용하지 않은채로 지연 로딩을 유지하도록 했음.
-    // 과도한 N+1 예시: Rooms를 JPA의 findAll()로 호출하고, 각 Room을 순회하며 room.getUserRoomList.get내부속성()으로 접근하는 경우.
+    // Room 조회시 Room.userRoomList N+1 문제 해결 ==> Eager 조회 : '방의 입장인원 전원 퇴장여부 확인 용도', Lazy 조회 : '기본 지연로딩 용도'
     @OneToMany(mappedBy = "room")  // Room-UserRoom 양방향매핑 (읽기 전용 필드)
-    private List<UserRoom> userRoomList = new ArrayList<>();  // '방의 입장인원 전원 퇴장여부 확인 용도'에 활용.
+    private List<UserRoom> userRoomList = new ArrayList<>();
 
 
     @Builder(builderClassName = "RoomSaveBuilder", builderMethodName = "RoomSaveBuilder")
diff --git a/src/main/java/com/sajang/devracebackend/domain/User.java b/src/main/java/com/sajang/devracebackend/domain/User.java
index bbbc025..6340ce9 100644
--- a/src/main/java/com/sajang/devracebackend/domain/User.java
+++ b/src/main/java/com/sajang/devracebackend/domain/User.java
@@ -47,10 +47,9 @@ public class User extends BaseEntity implements Serializable {
     @Column(name = "refresh_token")
     private String refreshToken;
 
-    // 밑처럼 과도한 N+1 문제를 유발할 서비스 로직이 없을뿐더러 활용 빈도수도 낮기때문에, fetch join이나 @EntityGraph를 사용하지 않은채로 지연 로딩을 유지하도록 했음.
-    // 과도한 N+1 예시: Users를 JPA의 findAll()로 호출하고, 각 User를 순회하며 user.getUserRoomList.get내부속성()으로 접근하는 경우.
+    // User 조회시 User.userRoomList N+1 문제 해결 ==> Eager 조회 : '사용자의 참여중인 방 찾는 용도', Lazy 조회 : '기본 지연로딩 용도 & 회원탈퇴 용도'
     @OneToMany(mappedBy = "user")  // User-UserRoom 양방향매핑 (읽기 전용 필드)
-    private List<UserRoom> userRoomList = new ArrayList<>();  // '사용자의 참여중인 방 찾는 용도 & 회원탈퇴 용도'에 활용.
+    private List<UserRoom> userRoomList = new ArrayList<>();
 
 
     @Builder(builderClassName = "UserSaveBuilder", builderMethodName = "UserSaveBuilder")
diff --git a/src/main/java/com/sajang/devracebackend/domain/mapping/UserRoom.java b/src/main/java/com/sajang/devracebackend/domain/mapping/UserRoom.java
index 0404215..e6ad223 100644
--- a/src/main/java/com/sajang/devracebackend/domain/mapping/UserRoom.java
+++ b/src/main/java/com/sajang/devracebackend/domain/mapping/UserRoom.java
@@ -39,11 +39,13 @@ public class UserRoom extends BaseEntity implements Serializable {
     @Column(name = "leave_time")
     private LocalDateTime leaveTime;  // 퇴장 시각 (반면, createdTime = 입장 시각)
 
+    // Eager 조회의 용도가 적어, 기본 Lazy 조회로만 사용함.
     @ManyToOne(fetch = FetchType.LAZY)  // User-UserRoom 양방향매핑
     @JoinColumn(name = "user_id")
     private User user;
 
-    @ManyToOne(fetch = FetchType.LAZY)  // Room-UserRoom 양방향매핑 (default로 Lazy를 적용하되, Eager가 필요할경우 따로 메소드를 만들어 사용함.)
+    // UserRoom 조회시 UserRoom.room N+1 문제 해결 ==> Eager 조회 : '@EntityGraph 적용 메소드 활용', Lazy 조회 : '기본 지연로딩 용도'
+    @ManyToOne(fetch = FetchType.LAZY)  // Room-UserRoom 양방향매핑
     @JoinColumn(name = "room_id")
     private Room room;
 
diff --git a/src/main/java/com/sajang/devracebackend/dto/room/RoomSaveResponseDto.java b/src/main/java/com/sajang/devracebackend/dto/room/RoomResponseDto.java
similarity index 87%
rename from src/main/java/com/sajang/devracebackend/dto/room/RoomSaveResponseDto.java
rename to src/main/java/com/sajang/devracebackend/dto/room/RoomResponseDto.java
index 938597f..54570f4 100644
--- a/src/main/java/com/sajang/devracebackend/dto/room/RoomSaveResponseDto.java
+++ b/src/main/java/com/sajang/devracebackend/dto/room/RoomResponseDto.java
@@ -9,7 +9,7 @@
 @Getter
 @NoArgsConstructor
 @AllArgsConstructor
-public class RoomSaveResponseDto {
+public class RoomResponseDto {
 
     private Long roomId;
 }
diff --git a/src/main/java/com/sajang/devracebackend/repository/RoomRepository.java b/src/main/java/com/sajang/devracebackend/repository/RoomRepository.java
index 5ba27ac..af4d442 100644
--- a/src/main/java/com/sajang/devracebackend/repository/RoomRepository.java
+++ b/src/main/java/com/sajang/devracebackend/repository/RoomRepository.java
@@ -3,5 +3,8 @@
 import com.sajang.devracebackend.domain.Room;
 import org.springframework.data.jpa.repository.JpaRepository;
 
+import java.util.Optional;
+
 public interface RoomRepository extends JpaRepository<Room, Long> {
+    Optional<Room> findByLink(String link);
 }
\ No newline at end of file
diff --git a/src/main/java/com/sajang/devracebackend/repository/UserRepository.java b/src/main/java/com/sajang/devracebackend/repository/UserRepository.java
index 73c471c..cd56c67 100644
--- a/src/main/java/com/sajang/devracebackend/repository/UserRepository.java
+++ b/src/main/java/com/sajang/devracebackend/repository/UserRepository.java
@@ -3,11 +3,20 @@
 import com.sajang.devracebackend.domain.User;
 import com.sajang.devracebackend.domain.enums.SocialType;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 
 import java.util.List;
 import java.util.Optional;
 
 public interface UserRepository extends JpaRepository<User, Long> {
+    // '@EntityGraph' 또는 'Fetch Join'을 통해 User 조회시, 내부의 Lazy 로딩으로 선언된 속성 또한 Eager로 한번에 조회.
+    // ==> N+1 문제 해결 (간단한 로직은 '@EntityGraph'로, 복잡한 로직이거나 기존 JPA 메소드와의 네이밍 충돌을 방지하고자하는 경우는 'Fetch Join'을 활용.)
+
+    // - Eager 조회 : 'User + User.userRoomList'
+    @Query("SELECT u FROM User u JOIN FETCH u.userRoomList WHERE u.id = :userId")
+    Optional<User> findByIdWithEagerUserRoomList(@Param("userId") Long userId);  // 기존의 JPA findById() 메소드를 @Override 하지않고 유지하기위해, @Query로 새로운 메소드 네이밍을 지어주었음. -> '@EntityGraph' 말고 'Fetch Join' 사용.
+
     Optional<User> findBySocialTypeAndSocialId(SocialType socialType, String socialId);  // '소셜 타입, 식별자'로 해당 회원을 찾기 위한 메소드 (차후 추가정보 입력 회원가입 가능)
     boolean existsByBojId(String bojId);
     List<User> findByIdIn(List<Long> userIdList);
diff --git a/src/main/java/com/sajang/devracebackend/repository/UserRoomRepository.java b/src/main/java/com/sajang/devracebackend/repository/UserRoomRepository.java
index 9445bb1..018d905 100644
--- a/src/main/java/com/sajang/devracebackend/repository/UserRoomRepository.java
+++ b/src/main/java/com/sajang/devracebackend/repository/UserRoomRepository.java
@@ -7,21 +7,36 @@
 import org.springframework.data.domain.Pageable;
 import org.springframework.data.jpa.repository.EntityGraph;
 import org.springframework.data.jpa.repository.JpaRepository;
+import org.springframework.data.jpa.repository.Query;
+import org.springframework.data.repository.query.Param;
 
 import java.util.Optional;
 
 public interface UserRoomRepository extends JpaRepository<UserRoom, Long> {
+    // '@EntityGraph' 또는 'Fetch Join'을 통해 UserRoom 조회시, 내부의 Lazy 로딩으로 선언된 속성 또한 Eager로 한번에 조회.
+    // ==> N+1 문제 해결 (간단한 로직은 '@EntityGraph'로, 복잡한 로직이거나 기존 JPA 메소드와의 네이밍 충돌을 방지하고자하는 경우는 'Fetch Join'을 활용.)
 
-    // 서비스 로직에 UserRoom과 내부의 Room 정보를 모두 조회하여 사용하는 경우가 많았기에, 이를 적용하였음.
-    // @EntityGraph를 통해 UserRoom 조회시, 내부의 Lazy 로딩으로 선언된 Room 또한 Eager로 한번에 조회하여, N+1 문제를 해결.
-    // ==> Eager 조회 : 'UserRoom + 내부 Room', Lazy 조회 : '내부 User'
-    @EntityGraph(attributePaths = {"room"})
-    Optional<UserRoom> findByUser_IdAndRoom_Id(Long userId, Long roomId);
+    // - Eager 조회 : 'UserRoom + UserRoom.room', Lazy 조회 : 'UserRoom.user'
+    @EntityGraph(attributePaths = {"room"})  // 반환값이 List가 아닌 고유한 하나의 값이기에, @EntityGraph임에도 DISTINCT 없이 작성했음.
+    Optional<UserRoom> findByUser_IdAndRoom_Id(Long userId, Long roomId);  // 이는 @Query가 아니므로, JPA네이밍 규칙에 영향을 받음.
+
+    // - Eager 조회 : 'UserRoom + UserRoom.room + UserRoom.room.userRoomList', Lazy 조회 : 'UserRoom.user'
+    @Query("SELECT ur FROM UserRoom ur JOIN FETCH ur.room r JOIN FETCH r.userRoomList WHERE ur.user.id = :userId AND ur.room.id = :roomId")
+    Optional<UserRoom> findByUser_IdAndRoom_IdWithUserRoomList(@Param("userId") Long userId, @Param("roomId") Long roomId);  // @Query 이므로, With문처럼 JPA네이밍 규칙을 지키지않아도됨.
+
+    // - Eager 조회 : 'UserRoom + UserRoom.room + UserRoom.room.problem', Lazy 조회 : 'UserRoom.user'
+    @Query("SELECT ur FROM UserRoom ur JOIN FETCH ur.room r JOIN FETCH r.problem WHERE ur.user.id = :userId AND ur.room.id = :roomId")
+    Optional<UserRoom> findByUser_IdAndRoom_IdWithProblem(@Param("userId") Long userId, @Param("roomId") Long roomId);  // @Query 이므로, With문처럼 JPA네이밍 규칙을 지키지않아도됨.
 
     boolean existsByUserAndRoom(User user, Room room);
 
-    Page<UserRoom> findAllByIsLeaveAndUser_Id(Integer isLeave, Long userId, Pageable pageable);
-    Page<UserRoom> findAllByIsLeaveAndIsPass(Integer isLeave, Integer isPass, Pageable pageable);
-    Page<UserRoom> findAllByIsLeaveAndRoom_Problem_Number(Integer isLeave, Integer number, Pageable pageable);
-    Page<UserRoom> findAllByRoom_Link(String link, Pageable pageable);
+    // 밑의 3가지 메소드 모두, 페이징에서 OneToMany 속성을 Eager 조회시키지 않을것이기에, '중복 제거 처리' 및 '배치 사이즈 선언'을 하지 않았음.
+    @EntityGraph(attributePaths = {"room", "room.problem"})
+    Page<UserRoom> findAllByUser_IdAndIsLeave(Long userId, Integer isLeave, Pageable pageable);
+
+    @EntityGraph(attributePaths = {"room", "room.problem"})
+    Page<UserRoom> findAllByUser_IdAndIsLeaveAndIsPass(Long userId, Integer isLeave, Integer isPass, Pageable pageable);
+
+    @EntityGraph(attributePaths = {"room", "room.problem"})
+    Page<UserRoom> findAllByUser_IdAndIsLeaveAndRoom_Problem_Number(Long userId, Integer isLeave, Integer number, Pageable pageable);
 }
\ No newline at end of file
diff --git a/src/main/java/com/sajang/devracebackend/service/RoomService.java b/src/main/java/com/sajang/devracebackend/service/RoomService.java
index 99b3ef5..95e789b 100644
--- a/src/main/java/com/sajang/devracebackend/service/RoomService.java
+++ b/src/main/java/com/sajang/devracebackend/service/RoomService.java
@@ -3,12 +3,13 @@
 import com.sajang.devracebackend.domain.Room;
 import com.sajang.devracebackend.dto.problem.ProblemSaveRequestDto;
 import com.sajang.devracebackend.dto.room.RoomCheckStateResponseDto;
-import com.sajang.devracebackend.dto.room.RoomSaveResponseDto;
+import com.sajang.devracebackend.dto.room.RoomResponseDto;
 
 import java.io.IOException;
 
 public interface RoomService {
     Room findRoom(Long roomId);
-    RoomSaveResponseDto createRoom(ProblemSaveRequestDto problemSaveRequestDto) throws IOException;
+    RoomResponseDto findRoomByLink(String link);
+    RoomResponseDto createRoom(ProblemSaveRequestDto problemSaveRequestDto) throws IOException;
     RoomCheckStateResponseDto checkState(Long roomId);
 }
diff --git a/src/main/java/com/sajang/devracebackend/service/UserRoomService.java b/src/main/java/com/sajang/devracebackend/service/UserRoomService.java
index 69da67f..84a9417 100644
--- a/src/main/java/com/sajang/devracebackend/service/UserRoomService.java
+++ b/src/main/java/com/sajang/devracebackend/service/UserRoomService.java
@@ -11,12 +11,12 @@
 import org.springframework.data.domain.Pageable;
 
 public interface UserRoomService {
-    UserRoom findUserRoom(Long userId, Long roomId);  // Eager 조회 : 'UserRoom + 내부 Room', Lazy 조회 : '내부 User'
+    UserRoom findUserRoomWithEagerRoom(Long userId, Long roomId, boolean isIncludeUserRoomList, boolean isIncludeProblem);
     RoomWaitResponseDto userWaitRoom(RoomWaitRequestDto roomWaitRequestDto);
     void usersEnterRoom(Long roomId);
     void userStopWaitRoom(Long roomId);
     SolvingPageResponseDto loadSolvingPage(Long roomId);
     RoomCheckAccessResponseDto checkAccess(Long roomId);
     void passSolvingProblem(Long roomId, UserPassRequestDto userPassRequestDto);
-    Page<CodeRoomResponseDto> findCodeRoom(Integer isPass, Integer number, String link, Pageable pageable);
+    Page<CodeRoomResponseDto> findCodeRooms(Integer isPass, Integer number, Pageable pageable);
 }
diff --git a/src/main/java/com/sajang/devracebackend/service/UserService.java b/src/main/java/com/sajang/devracebackend/service/UserService.java
index 8fa766c..8431c1f 100644
--- a/src/main/java/com/sajang/devracebackend/service/UserService.java
+++ b/src/main/java/com/sajang/devracebackend/service/UserService.java
@@ -13,7 +13,7 @@
 public interface UserService {
     User findUser(Long userId);
     User findLoginUser();
-    <T> List<T> findUsersOriginal(List<Long> userIdList, Boolean isDto);
+    <T> List<T> findUsersOriginal(List<Long> userIdList, boolean isDto);
     UserResponseDto findUserProfile();
     void updateUserProfile(MultipartFile imageFile, UserUpdateRequestDto userUpdateRequestDto) throws IOException;
     UserSolvedResponseDto checkUserSolvedCount();
diff --git a/src/main/java/com/sajang/devracebackend/service/impl/AuthServiceImpl.java b/src/main/java/com/sajang/devracebackend/service/impl/AuthServiceImpl.java
index 623a405..febd5bb 100644
--- a/src/main/java/com/sajang/devracebackend/service/impl/AuthServiceImpl.java
+++ b/src/main/java/com/sajang/devracebackend/service/impl/AuthServiceImpl.java
@@ -43,7 +43,7 @@ public SignupResponseDto signup(MultipartFile imageFile, SignupRequestDto signup
         // - 기본사진으로 변경O : if 'imageFile == null && signupRequestDto.getIsImageChange() == 1' --> AWS S3 업로드X & User imageUrl값 null로 업데이트
 
         if(signupRequestDto.getBojId() == null) {
-            throw new Exception400.UserBadRequest("회원가입 백준id null 에러");
+            throw new Exception400.UserBadRequest("회원가입 bojId==null 에러");
         }
         if(userRepository.existsByBojId(signupRequestDto.getBojId()) == true) {  // 이미 해당 백준id로 가입한 사용자가 존재하는경우, 예외 처리.
             throw new Exception400.BojIdDuplicate(signupRequestDto.getBojId());
diff --git a/src/main/java/com/sajang/devracebackend/service/impl/ChatServiceImpl.java b/src/main/java/com/sajang/devracebackend/service/impl/ChatServiceImpl.java
index 8fd0018..cdd6f80 100644
--- a/src/main/java/com/sajang/devracebackend/service/impl/ChatServiceImpl.java
+++ b/src/main/java/com/sajang/devracebackend/service/impl/ChatServiceImpl.java
@@ -81,7 +81,9 @@ else if(chatRequestDto.getMessageType().equals(MessageType.RANK)) {
     @Transactional(readOnly = true)
     @Override
     public Slice<ChatResponseDto> findChatsByRoom(Long roomId, Pageable pageable) {
-        UserRoom userRoom = userRoomService.findUserRoom(SecurityUtil.getCurrentMemberId(), roomId);
+
+        // 'UserRoom.room' Eager 로딩 (N+1 문제 해결)
+        UserRoom userRoom = userRoomService.findUserRoomWithEagerRoom(SecurityUtil.getCurrentMemberId(), roomId, false, false);
         LocalDateTime leaveTime = userRoom.getLeaveTime();
 
         // 퇴장한 경우, 본인 퇴장시각 이하까지의 채팅 내역 조회
diff --git a/src/main/java/com/sajang/devracebackend/service/impl/RoomServiceImpl.java b/src/main/java/com/sajang/devracebackend/service/impl/RoomServiceImpl.java
index 3055d14..706f5df 100644
--- a/src/main/java/com/sajang/devracebackend/service/impl/RoomServiceImpl.java
+++ b/src/main/java/com/sajang/devracebackend/service/impl/RoomServiceImpl.java
@@ -4,9 +4,10 @@
 import com.sajang.devracebackend.domain.Room;
 import com.sajang.devracebackend.dto.problem.ProblemSaveRequestDto;
 import com.sajang.devracebackend.dto.room.RoomCheckStateResponseDto;
-import com.sajang.devracebackend.dto.room.RoomSaveResponseDto;
+import com.sajang.devracebackend.dto.room.RoomResponseDto;
 import com.sajang.devracebackend.dto.user.UserResponseDto;
 import com.sajang.devracebackend.repository.*;
+import com.sajang.devracebackend.response.exception.Exception400;
 import com.sajang.devracebackend.response.exception.Exception404;
 import com.sajang.devracebackend.service.ProblemService;
 import com.sajang.devracebackend.service.RoomService;
@@ -34,12 +35,25 @@ public class RoomServiceImpl implements RoomService {
     @Override
     public Room findRoom(Long roomId) {
         return roomRepository.findById(roomId).orElseThrow(
-                ()->new Exception404.NoSuchRoom(String.format("roomId = %d", roomId)));
+                () -> new Exception404.NoSuchRoom(String.format("roomId = %d", roomId)));
+    }
+
+    @Transactional(readOnly = true)
+    @Override
+    public RoomResponseDto findRoomByLink(String link) {
+        if(link == null) throw new Exception400.RoomBadRequest("방 조회 link==null 에러");
+
+        Room room = roomRepository.findByLink(link).orElseThrow(
+                () -> new Exception404.NoSuchRoom("link = " + link));
+
+        return RoomResponseDto.builder()
+                .roomId(room.getId())
+                .build();
     }
 
     @Transactional
     @Override
-    public RoomSaveResponseDto createRoom(ProblemSaveRequestDto problemSaveRequestDto) throws IOException {
+    public RoomResponseDto createRoom(ProblemSaveRequestDto problemSaveRequestDto) throws IOException {
         Integer problemNumber = problemSaveRequestDto.getProblemNumber();
 
         Problem problem = problemRepository.findByNumber(problemNumber)
@@ -59,11 +73,11 @@ public RoomSaveResponseDto createRoom(ProblemSaveRequestDto problemSaveRequestDt
                 .problem(problem)
                 .build();
         Long roomId = roomRepository.save(room).getId();
-        RoomSaveResponseDto roomSaveResponseDto = RoomSaveResponseDto.builder()
+        RoomResponseDto roomResponseDto = RoomResponseDto.builder()
                 .roomId(roomId)
                 .build();
 
-        return roomSaveResponseDto;
+        return roomResponseDto;
     }
 
     @Transactional(readOnly = true)
diff --git a/src/main/java/com/sajang/devracebackend/service/impl/UserRoomServiceImpl.java b/src/main/java/com/sajang/devracebackend/service/impl/UserRoomServiceImpl.java
index 77a80a2..5e4cb2a 100644
--- a/src/main/java/com/sajang/devracebackend/service/impl/UserRoomServiceImpl.java
+++ b/src/main/java/com/sajang/devracebackend/service/impl/UserRoomServiceImpl.java
@@ -30,6 +30,7 @@
 import java.time.LocalDateTime;
 import java.util.List;
 import java.util.Optional;
+import java.util.function.BiFunction;
 import java.util.stream.Collectors;
 
 @Service
@@ -42,14 +43,27 @@ public class UserRoomServiceImpl implements UserRoomService {
     private final ChatRepository chatRepository;
 
 
-    // 서비스 로직에 UserRoom과 내부의 Room 정보를 모두 조회하여 사용하는 경우가 많았기에, 이를 적용하였음.
-    // @EntityGraph를 통해 UserRoom 조회시, 내부의 Lazy 로딩으로 선언된 Room 또한 Eager로 한번에 조회하여, N+1 문제를 해결.
-    // ==> Eager 조회 : 'UserRoom + 내부 Room', Lazy 조회 : '내부 User'
     @Transactional(readOnly = true)
     @Override
-    public UserRoom findUserRoom(Long userId, Long roomId) {
-        return userRoomRepository.findByUser_IdAndRoom_Id(userId, roomId).orElseThrow(
-                ()->new Exception404.NoSuchUserRoom(String.format("userId = %d & roomId = %d", userId, roomId)));
+    public UserRoom findUserRoomWithEagerRoom(Long userId, Long roomId, boolean isIncludeUserRoomList, boolean isIncludeProblem) {
+        // 서비스 로직에 UserRoom과 내부의 Room 정보를 모두 조회하여 사용하는 경우가 많았기에, 이 코드를 작성함.
+        // '@EntityGraph' 또는 'Fetch Join'을 통해 UserRoom 조회시, 내부의 Lazy 로딩으로 선언된 속성 또한 Eager로 한번에 조회하여 N+1 문제를 해결함.
+
+        if(!isIncludeUserRoomList && !isIncludeProblem) {
+            // - Eager 조회 : 'UserRoom + UserRoom.room', Lazy 조회 : 'UserRoom.user'
+            return findUserRoom(userId, roomId, userRoomRepository::findByUser_IdAndRoom_Id);
+        }
+        else if(isIncludeUserRoomList && !isIncludeProblem) {
+            // - Eager 조회 : 'UserRoom + UserRoom.room + UserRoom.room.userRoomList', Lazy 조회 : 'UserRoom.user'
+            return findUserRoom(userId, roomId, userRoomRepository::findByUser_IdAndRoom_IdWithUserRoomList);
+        }
+        else if(!isIncludeUserRoomList && isIncludeProblem) {
+            // - Eager 조회 : 'UserRoom + UserRoom.room + UserRoom.room.problem', Lazy 조회 : 'UserRoom.user'
+            return findUserRoom(userId, roomId, userRoomRepository::findByUser_IdAndRoom_IdWithProblem);
+        }
+        else {  // 잘못된 파라미터 입력
+            throw new IllegalArgumentException("메소드에 잘못된 파라미터를 입력하였습니다.");
+        }
     }
 
     @Transactional
@@ -129,44 +143,36 @@ public void userStopWaitRoom(Long roomId) {
     @Transactional(readOnly = true)
     @Override
     public SolvingPageResponseDto loadSolvingPage(Long roomId) {
-        UserRoom userRoom = findUserRoom(SecurityUtil.getCurrentMemberId(), roomId);  // 어차피 문제풀이 페이지는 입장 이후이기에, 부모 Room을 갖고있는 자식 UserRoom은 반드시 존재함.
 
-        List<Long> rankUserIdList = userRoom.getRoom().getWaiting();  // @EntityGraph로 UserRoom 내부의 Room은 Eager 로딩 처리되어, N+1 문제가 발생하지 않음.
+        // 'UserRoom.room & UserRoom.room.problem' Eager 로딩 (N+1 문제 해결)
+        UserRoom userRoom = findUserRoomWithEagerRoom(SecurityUtil.getCurrentMemberId(), roomId, false, true);  // 어차피 문제풀이 페이지는 입장 이후이기에, 부모 Room을 갖고있는 자식 UserRoom은 반드시 존재함.
+
+        List<Long> rankUserIdList = userRoom.getRoom().getWaiting();
         List<UserResponseDto> rankUserDtoList = userService.findUsersOriginal(rankUserIdList, true);
 
-        return new SolvingPageResponseDto(userRoom, rankUserDtoList);  // UserRoom의 Room의 Problem은 호출 빈도수가 낮기도하고, JPA메소드 네이밍이 겹치기에, eager 적용을 하지 않았음.
+        return new SolvingPageResponseDto(userRoom, rankUserDtoList);  // Fetch Join으로 UserRoom 내부의 UserRoom.room과 UserRoom.room.problem은 Eager 로딩 처리되어, N+1 문제가 발생하지 않음.
     }
 
     @Transactional(readOnly = true)
     @Override
     public RoomCheckAccessResponseDto checkAccess(Long roomId) {
-//        System.out.println("========== !!! 메소드 시작 !!! ==========\n");
 
-//        System.out.println("===== UserRoom 조회 =====");
+        // 'UserRoom.room' Eager 로딩 (N+1 문제 해결)
         Optional<UserRoom> optionalUserRoom = userRoomRepository.findByUser_IdAndRoom_Id(SecurityUtil.getCurrentMemberId(), roomId);
-//        System.out.println("===== UserRoom 조회 완료. [1번의 쿼리 발생] =====\n");
 
         // UserRoom이 존재하면 해당 정보 사용. 그렇지 않다면 DB에 Room 조회 쿼리 날림.
-//        System.out.println("===== UserRoom.getRoom() 실행 =====");
         Room room = optionalUserRoom
                 .map(UserRoom::getRoom)  // 이 시점에는 아직 @EntityGraph의 영향을 받지않아, 아직 조회 쿼리가 1번으로 유지됨.
                 .orElseGet(() -> roomService.findRoom(roomId));
-//        System.out.println("===== UserRoom의 Room을 가져오지만 Room 내부의 변수는 사용하지않음. [추가쿼리 발생 X] =====\n");
 
         Boolean isExistUserRoom = optionalUserRoom.isPresent();
-//        System.out.println("===== UserRoom.getIsLeave() 실행 =====");
         Integer isLeave = optionalUserRoom.map(UserRoom::getIsLeave).orElse(null);  // UserRoom이 없다면 isLeave는 null
-//        System.out.println("===== UserRoom의 Room 외의 타변수를 사용. [추가쿼리 발생 X] =====\n");
 
-//        System.out.println("===== UserRoom.getRoom().getRoomState() 실행 =====");
         RoomCheckAccessResponseDto roomCheckAccessResponseDto = RoomCheckAccessResponseDto.builder()
                 .isExistUserRoom(isExistUserRoom)
                 .roomState(room.getRoomState())  // @EntityGraph로 UserRoom 내부의 Room은 Eager 로딩 처리되어, N+1 문제가 발생하지 않음.
                 .isLeave(isLeave)
                 .build();
-//        System.out.println("===== UserRoom의 Room 내부의 변수를 사용. [@EntityGraph 미처리시 추가쿼리 발생 O] =====\n");
-
-//        System.out.println("========== !!! 메소드 종료 !!! ==========");
 
         return roomCheckAccessResponseDto;
     }
@@ -174,11 +180,13 @@ public RoomCheckAccessResponseDto checkAccess(Long roomId) {
     @Transactional
     @Override
     public void passSolvingProblem(Long roomId, UserPassRequestDto userPassRequestDto) {
-        UserRoom userRoom = findUserRoom(SecurityUtil.getCurrentMemberId(), roomId);  // 어차피 문제풀이 페이지는 입장 이후이기에, 부모 Room을 갖고있는 자식 UserRoom은 반드시 존재함.
-        Room room = userRoom.getRoom();  // 이 시점에는 아직 @EntityGraph의 영향을 받지않아, 아직 조회 쿼리가 1번으로 유지됨.
+
+        // 'UserRoom.room & UserRoom.userRoomList' Eager 로딩 (N+1 문제 해결)
+        UserRoom userRoom = findUserRoomWithEagerRoom(SecurityUtil.getCurrentMemberId(), roomId, true, false);  // 어차피 문제풀이 페이지는 입장 이후이기에, 부모 Room을 갖고있는 자식 UserRoom은 반드시 존재함.
+        Room room = userRoom.getRoom();  // 이 시점에는 아직 Fetch Join의 영향을 받지않아, 아직 조회 쿼리가 1번으로 유지됨.
 
         userRoom.updateCode(userPassRequestDto.getCode());
-        userRoom.updateIsLeave(1);
+        userRoom.updateIsLeave(1);  // 더티체킹으로 update가 DB에 바로 반영되지않지만, UserRoom은 동일 트랜잭션 내의 JPA 영속성 컨텍스트가 관리하는 상위 엔티티이므로, 이후 호출되는 하위 'UserRoom.getRoom().getUserRoomList()'에서도 update상태 확인이 가능함.
         userRoom.updateLeaveTime(LocalDateTime.now());
 
         if(userPassRequestDto.getIsRetry() == 0 || (userPassRequestDto.getIsRetry() == 1 && userPassRequestDto.getIsPass() == 1)) {
@@ -186,28 +194,27 @@ public void passSolvingProblem(Long roomId, UserPassRequestDto userPassRequestDt
             userRoom.updateIsPass(userPassRequestDto.getIsPass());
         }
 
-        List<UserRoom> userRoomList = room.getUserRoomList();  // @EntityGraph로 UserRoom 내부의 Room은 Eager 로딩 처리되어, N+1 문제가 발생하지 않음.
-        Boolean isLeaveAllUsers = userRoomList.stream()
-                .allMatch(enterUserRoom -> enterUserRoom.getIsLeave() == 1);  // 입장했던 모든 유저의 isLeave 값이 1인지 확인
+        List<UserRoom> userRoomList = room.getUserRoomList();  // Fetch Join으로 UserRoom 내부의 Room은 Eager 로딩 처리되어, N+1 문제가 발생하지 않음.
+        Boolean isLeaveAllUsers = userRoomList.stream()  // Fetch Join으로 UserRoom 내부의 Room.userRoomList는 Eager 로딩 처리되어, N+1 문제가 발생하지 않음.
+                .allMatch(enterUserRoom -> enterUserRoom.getIsLeave() == 1);  // 입장했던 모든 유저의 isLeave 값이 1인지 확인 (DB에는 위의 updateIsLeave(1)가 아직 반영되지않았지만, 동일 트랜잭션 내라서 바로 확인이 가능함.)
         if(isLeaveAllUsers == true) room.updateRoomState(RoomState.FINISH);
     }
 
     @Transactional(readOnly = true)
     @Override
-    public Page<CodeRoomResponseDto> findCodeRoom(Integer isPass, Integer number, String link, Pageable pageable) {
+    public Page<CodeRoomResponseDto> findCodeRooms(Integer isPass, Integer number, Pageable pageable) {
+        Long loginUserId = SecurityUtil.getCurrentMemberId();
         Page<UserRoom> userRoomPage;
 
-        if(isPass == null && number == null && link == null) {  // 전체 정렬 조회의 경우
-            userRoomPage = userRoomRepository.findAllByIsLeaveAndUser_Id(1, SecurityUtil.getCurrentMemberId(), pageable);
-        }
-        else if(isPass != null && number == null && link == null) {  // 성공or실패 정렬 조회의 경우
-            userRoomPage = userRoomRepository.findAllByIsLeaveAndIsPass(1, isPass, pageable);
+        // 'UserRoom.room & UserRoom.room.problem' Eager 로딩 (N+1 문제 해결)
+        if(isPass == null && number == null) {  // 전체 정렬 조회의 경우
+            userRoomPage = userRoomRepository.findAllByUser_IdAndIsLeave(loginUserId, 1, pageable);
         }
-        else if(isPass == null && number != null && link == null) {  // 문제번호 검색 조회의 경우
-            userRoomPage = userRoomRepository.findAllByIsLeaveAndRoom_Problem_Number(1, number, pageable);
+        else if(isPass != null && number == null) {  // 성공or실패 정렬 조회의 경우
+            userRoomPage = userRoomRepository.findAllByUser_IdAndIsLeaveAndIsPass(loginUserId, 1, isPass, pageable);
         }
-        else if(isPass == null && number == null && link != null) {  // 초대링크 탐색 조회의 경우
-            userRoomPage = userRoomRepository.findAllByRoom_Link(link, pageable);
+        else if(isPass == null && number != null) {  // 문제번호 검색 조회의 경우
+            userRoomPage = userRoomRepository.findAllByUser_IdAndIsLeaveAndRoom_Problem_Number(loginUserId, 1, number, pageable);
         }
         else {  // 잘못된 URI
             throw new Exception400.UserRoomBadRequest("잘못된 쿼리파라미터로 API를 요청하였습니다.");
@@ -215,4 +222,12 @@ else if(isPass == null && number == null && link != null) {  // 초대링크 탐
 
         return userRoomPage.map(userRoom -> new CodeRoomResponseDto(userRoom));
     }
+
+
+    // ========== 유틸성 메소드 ========== //
+
+    private static UserRoom findUserRoom(Long userId, Long roomId, BiFunction<Long, Long, Optional<UserRoom>> function) {  // userId,roomId,함수를 받아서 UserRoom을 찾는 메소드 (dto가 아닌 entity를 반환하므로, private 접근제어자 사용.)
+        return function.apply(userId, roomId).orElseThrow(
+                () -> new Exception404.NoSuchUserRoom(String.format("userId = %d & roomId = %d", userId, roomId)));
+    }
 }
diff --git a/src/main/java/com/sajang/devracebackend/service/impl/UserServiceImpl.java b/src/main/java/com/sajang/devracebackend/service/impl/UserServiceImpl.java
index 5db2351..f07a55a 100644
--- a/src/main/java/com/sajang/devracebackend/service/impl/UserServiceImpl.java
+++ b/src/main/java/com/sajang/devracebackend/service/impl/UserServiceImpl.java
@@ -1,7 +1,6 @@
 package com.sajang.devracebackend.service.impl;
 
 import com.sajang.devracebackend.domain.User;
-import com.sajang.devracebackend.domain.mapping.UserRoom;
 import com.sajang.devracebackend.dto.user.UserCheckRoomResponseDto;
 import com.sajang.devracebackend.dto.user.UserResponseDto;
 import com.sajang.devracebackend.dto.user.UserSolvedResponseDto;
@@ -22,7 +21,6 @@
 import java.io.IOException;
 import java.util.List;
 import java.util.Map;
-import java.util.Optional;
 import java.util.stream.Collectors;
 
 @Service
@@ -37,7 +35,7 @@ public class UserServiceImpl implements UserService {
     @Override
     public User findUser(Long userId) {
         return userRepository.findById(userId).orElseThrow(
-                ()->new Exception404.NoSuchUser(String.format("userId = %d", userId)));
+                () -> new Exception404.NoSuchUser(String.format("userId = %d", userId)));
     }
 
     @Transactional(readOnly = true)
@@ -50,7 +48,7 @@ public User findLoginUser() {
 
     @Transactional(readOnly = true)
     @Override
-    public <T> List<T> findUsersOriginal(List<Long> userIdList, Boolean isDto) {  // 기존 userId리스트의 순서를 보장하는 User&UserDto리스트 반환 메소드
+    public <T> List<T> findUsersOriginal(List<Long> userIdList, boolean isDto) {  // 기존 userId리스트의 순서를 보장하는 User&UserDto리스트 반환 메소드
         List<User> userList = userRepository.findByIdIn(userIdList);
         Map<Long, User> userMap = userList.stream()
                 .collect(Collectors.toMap(User::getId, user -> user));
@@ -106,26 +104,22 @@ public UserSolvedResponseDto checkUserSolvedCount() {
     @Transactional(readOnly = true)
     @Override
     public UserCheckRoomResponseDto checkCurrentRoom() {
-        User user = findLoginUser();
 
-        Optional<UserRoom> optionalUserRoom = user.getUserRoomList().stream()
+        // 'User.userRoomList' Eager 로딩 (N+1 문제 해결)
+        User user = userRepository.findByIdWithEagerUserRoomList(SecurityUtil.getCurrentMemberId()).orElseThrow(
+                () -> new Exception404.NoSuchUser(String.format("userId = %d", SecurityUtil.getCurrentMemberId())));
+
+        UserCheckRoomResponseDto userCheckRoomResponseDto = user.getUserRoomList().stream()
                 .filter(userRoom -> userRoom.getIsLeave() == 0)  // getIsLeave() 값이 0인 경우만 필터링 (참여중인 방 찾기)
-                .findFirst();
-        UserRoom userRoom = optionalUserRoom.orElse(null);
-
-        UserCheckRoomResponseDto userCheckRoomResponseDto;
-        if(userRoom == null) {  // 참여중인 방이 없을때 X
-            userCheckRoomResponseDto = UserCheckRoomResponseDto.builder()
-                    .isExistRoom(false)
-                    .roomId(null)
-                    .build();
-        }
-        else {  // 참여중인 방이 있을때 O
-            userCheckRoomResponseDto = UserCheckRoomResponseDto.builder()
-                    .isExistRoom(true)
-                    .roomId(userRoom.getRoom().getId())
-                    .build();
-        }
+                .findFirst()
+                .map(userRoom -> UserCheckRoomResponseDto.builder()  // 참여중인 방이 있을때 O
+                        .isExistRoom(true)
+                        .roomId(userRoom.getRoom().getId())  // User.userRoomList.room까지 Eager 처리하면 참여중인 방이 없을시의 성능 하락이 심하기에, 처리하지않음.
+                        .build())
+                .orElse(UserCheckRoomResponseDto.builder()  // 참여중인 방이 없을때 X
+                        .isExistRoom(false)
+                        .roomId(null)
+                        .build());
 
         return userCheckRoomResponseDto;
     }
@@ -133,7 +127,7 @@ public UserCheckRoomResponseDto checkCurrentRoom() {
 
     // ========== 유틸성 메소드 ========== //
 
-    public static UserSolvedResponseDto getSolvedCount(String bojId) {  // WebClient로 외부 solved API 호출 메소드
+    public static UserSolvedResponseDto getSolvedCount(String bojId) {  // WebClient로 외부 solved API 호출 메소드 (entity가 아닌 dto를 반환하므로, public 접근제어자 가능.)
         try {
             WebClient webClient = WebClient.builder()
                     .baseUrl("https://solved.ac/api/v3")