diff --git a/src/main/java/com/project/trainingdiary/controller/DietController.java b/src/main/java/com/project/trainingdiary/controller/DietController.java
index 51b1ed7b..656b77c4 100644
--- a/src/main/java/com/project/trainingdiary/controller/DietController.java
+++ b/src/main/java/com/project/trainingdiary/controller/DietController.java
@@ -42,6 +42,7 @@ public class DietController {
   )
   @ApiResponses(value = {
       @ApiResponse(responseCode = "200", description = "성공"),
+      @ApiResponse(responseCode = "415", description = "유효하지 않은 미디어 타입 입니다.")
   })
   @PreAuthorize("hasRole('TRAINEE')")
   @PostMapping(consumes = MediaType.MULTIPART_FORM_DATA_VALUE)
@@ -65,6 +66,7 @@ public ResponseEntity<Void> createDiet(
   @GetMapping("{id}")
   @ApiResponses(value = {
       @ApiResponse(responseCode = "200", description = "성공"),
+      @ApiResponse(responseCode = "403", description = "트레이너랑 트레이니 사이의 계약이 없습니다.")
   })
   @PreAuthorize("hasRole('TRAINER') or hasRole('TRAINEE')")
   public ResponseEntity<Page<DietImageResponseDto>> getTraineeDiets(
@@ -84,6 +86,7 @@ public ResponseEntity<Page<DietImageResponseDto>> getTraineeDiets(
   )
   @ApiResponses(value = {
       @ApiResponse(responseCode = "200", description = "성공"),
+      @ApiResponse(responseCode = "403", description = "트레이너랑 트레이니 사이의 계약이 없습니다.")
   })
   @PreAuthorize("hasRole('TRAINER') or hasRole('TRAINEE')")
   @GetMapping("{id}/details")
diff --git a/src/main/java/com/project/trainingdiary/dto/response/diet/DietDetailsInfoResponseDto.java b/src/main/java/com/project/trainingdiary/dto/response/diet/DietDetailsInfoResponseDto.java
index 49dd9dbf..9765d8db 100644
--- a/src/main/java/com/project/trainingdiary/dto/response/diet/DietDetailsInfoResponseDto.java
+++ b/src/main/java/com/project/trainingdiary/dto/response/diet/DietDetailsInfoResponseDto.java
@@ -3,6 +3,7 @@
 import com.project.trainingdiary.dto.response.comment.CommentDto;
 import com.project.trainingdiary.entity.CommentEntity;
 import com.project.trainingdiary.entity.DietEntity;
+import com.project.trainingdiary.util.ConvertCloudFrontUrlUtil;
 import java.time.LocalDate;
 import java.util.List;
 import lombok.Builder;
@@ -18,20 +19,19 @@ public class DietDetailsInfoResponseDto {
   private List<CommentDto> comments;
   private LocalDate createdDate;
 
-  public static DietDetailsInfoResponseDto of(DietEntity diet,
-      List<CommentEntity> comments) {
+  public static DietDetailsInfoResponseDto of(DietEntity diet, List<CommentEntity> comments) {
 
-    List<CommentDto> commentDto = comments.stream()
-        .sorted((a, b) -> b.getCreatedAt().compareTo(a.getCreatedAt()))
-        .map(CommentDto::fromEntity)
+    List<CommentDto> commentDtoList = comments.stream()
+        .sorted((a, b) -> b.getCreatedAt().compareTo(a.getCreatedAt())) // 최신 댓글이 위로 오도록 정렬
+        .map(CommentDto::fromEntity) // CommentEntity를 CommentDto로 변환
         .toList();
 
     return DietDetailsInfoResponseDto.builder()
         .id(diet.getId())
-        .imageUrl(diet.getOriginalUrl())
+        .imageUrl(ConvertCloudFrontUrlUtil.convertToCloudFrontUrl(diet.getOriginalUrl()))
         .content(diet.getContent())
-        .comments(commentDto)
+        .comments(commentDtoList)
         .createdDate(diet.getCreatedAt().toLocalDate())
         .build();
   }
-}
+}
\ No newline at end of file
diff --git a/src/main/java/com/project/trainingdiary/dto/response/trainer/TraineeInfoResponseDto.java b/src/main/java/com/project/trainingdiary/dto/response/trainer/TraineeInfoResponseDto.java
index e5ca4307..3e840a5a 100644
--- a/src/main/java/com/project/trainingdiary/dto/response/trainer/TraineeInfoResponseDto.java
+++ b/src/main/java/com/project/trainingdiary/dto/response/trainer/TraineeInfoResponseDto.java
@@ -58,19 +58,22 @@ private static int calculateAge(LocalDate birthDate) {
     return birthDate != null ? Period.between(birthDate, LocalDate.now()).getYears() : 0;
   }
 
-  private static List<WeightHistoryDto> mapToWeightHistory(List<InBodyRecordHistoryEntity> inBodyRecords) {
+  private static List<WeightHistoryDto> mapToWeightHistory(
+      List<InBodyRecordHistoryEntity> inBodyRecords) {
     return inBodyRecords.stream()
         .map(WeightHistoryDto::fromEntity)
         .collect(Collectors.toList());
   }
 
-  private static List<BodyFatHistoryDto> mapToBodyFatHistory(List<InBodyRecordHistoryEntity> inBodyRecords) {
+  private static List<BodyFatHistoryDto> mapToBodyFatHistory(
+      List<InBodyRecordHistoryEntity> inBodyRecords) {
     return inBodyRecords.stream()
         .map(BodyFatHistoryDto::fromEntity)
         .collect(Collectors.toList());
   }
 
-  private static List<MuscleMassHistoryDto> mapToMuscleMassHistory(List<InBodyRecordHistoryEntity> inBodyRecords) {
+  private static List<MuscleMassHistoryDto> mapToMuscleMassHistory(
+      List<InBodyRecordHistoryEntity> inBodyRecords) {
     return inBodyRecords.stream()
         .map(MuscleMassHistoryDto::fromEntity)
         .collect(Collectors.toList());
diff --git a/src/main/java/com/project/trainingdiary/exception/ptcontract/PtContractNotExistException.java b/src/main/java/com/project/trainingdiary/exception/ptcontract/PtContractNotExistException.java
index 467f6abd..ca617411 100644
--- a/src/main/java/com/project/trainingdiary/exception/ptcontract/PtContractNotExistException.java
+++ b/src/main/java/com/project/trainingdiary/exception/ptcontract/PtContractNotExistException.java
@@ -6,6 +6,6 @@
 public class PtContractNotExistException extends GlobalException {
 
   public PtContractNotExistException() {
-    super(HttpStatus.NOT_FOUND, "계약이 없습니다.");
+    super(HttpStatus.FORBIDDEN, "계약이 없습니다.");
   }
 }
diff --git a/src/main/java/com/project/trainingdiary/provider/S3DietImageProvider.java b/src/main/java/com/project/trainingdiary/provider/S3DietImageProvider.java
new file mode 100644
index 00000000..658ddcc9
--- /dev/null
+++ b/src/main/java/com/project/trainingdiary/provider/S3DietImageProvider.java
@@ -0,0 +1,68 @@
+package com.project.trainingdiary.provider;
+
+import static com.project.trainingdiary.util.MediaUtil.getExtension;
+import static com.project.trainingdiary.util.MediaUtil.getMediaType;
+
+import com.project.trainingdiary.util.MediaUtil;
+import io.awspring.cloud.s3.ObjectMetadata;
+import io.awspring.cloud.s3.S3Operations;
+import io.awspring.cloud.s3.S3Resource;
+import java.awt.image.BufferedImage;
+import java.io.ByteArrayInputStream;
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.util.UUID;
+import javax.imageio.ImageIO;
+import lombok.RequiredArgsConstructor;
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.stereotype.Component;
+import org.springframework.web.multipart.MultipartFile;
+
+@RequiredArgsConstructor
+@Component
+public class S3DietImageProvider {
+
+  @Value("${spring.cloud.aws.s3.bucket}")
+  private String bucket;
+
+  private final S3Operations s3Operations;
+
+  public String uploadImageToS3(MultipartFile file) throws IOException {
+    BufferedImage originalImage = ImageIO.read(file.getInputStream());
+    BufferedImage resizedImage = MediaUtil.resizeOriginalImage(originalImage);
+    String extension = getExtension(MediaUtil.checkFileNameExist(file));
+    String key = UUID.randomUUID() + "." + extension;
+
+    try (ByteArrayOutputStream baos = new ByteArrayOutputStream()) {
+      ImageIO.write(resizedImage, extension, baos);
+      try (InputStream inputStream = new ByteArrayInputStream(baos.toByteArray())) {
+        S3Resource s3Resource = s3Operations.upload(bucket, key, inputStream,
+            ObjectMetadata.builder().contentType(file.getContentType()).build());
+        return s3Resource.getURL().toExternalForm();
+      }
+    }
+  }
+
+  public String uploadThumbnailToS3(MultipartFile file, String originalKey, String extension)
+      throws IOException {
+    BufferedImage originalImage = ImageIO.read(file.getInputStream());
+    BufferedImage thumbnailImage = MediaUtil.resizeThumbnail(originalImage);
+
+    try (ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream()) {
+      ImageIO.write(thumbnailImage, extension, byteArrayOutputStream);
+      try (InputStream inputStream = new ByteArrayInputStream(
+          byteArrayOutputStream.toByteArray())) {
+        String thumbnailKey = "thumb_" + originalKey.substring(originalKey.lastIndexOf("/") + 1);
+        S3Resource s3Resource = s3Operations.upload(bucket, thumbnailKey, inputStream,
+            ObjectMetadata.builder().contentType(getMediaType(extension)).build());
+        return s3Resource.getURL().toExternalForm();
+      }
+    }
+  }
+
+  public void deleteFileFromS3(String fileUrl) {
+    String fileKey = fileUrl.substring(fileUrl.lastIndexOf("/") + 1);
+    s3Operations.deleteObject(bucket, fileKey);
+  }
+}
diff --git a/src/main/java/com/project/trainingdiary/provider/S3Provider.java b/src/main/java/com/project/trainingdiary/provider/S3Provider.java
deleted file mode 100644
index 8146ed5c..00000000
--- a/src/main/java/com/project/trainingdiary/provider/S3Provider.java
+++ /dev/null
@@ -1,5 +0,0 @@
-package com.project.trainingdiary.provider;
-
-public class S3Provider {
-
-}
diff --git a/src/main/java/com/project/trainingdiary/service/DietService.java b/src/main/java/com/project/trainingdiary/service/DietService.java
index b0c59079..99c73439 100644
--- a/src/main/java/com/project/trainingdiary/service/DietService.java
+++ b/src/main/java/com/project/trainingdiary/service/DietService.java
@@ -13,11 +13,13 @@
 import com.project.trainingdiary.exception.user.UserNotFoundException;
 import com.project.trainingdiary.exception.workout.InvalidFileTypeException;
 import com.project.trainingdiary.model.type.UserRoleType;
+import com.project.trainingdiary.provider.S3DietImageProvider;
 import com.project.trainingdiary.repository.DietRepository;
 import com.project.trainingdiary.repository.TraineeRepository;
 import com.project.trainingdiary.repository.TrainerRepository;
 import com.project.trainingdiary.repository.ptContract.PtContractRepository;
-import com.project.trainingdiary.util.ImageUtil;
+import com.project.trainingdiary.util.ConvertCloudFrontUrlUtil;
+import com.project.trainingdiary.util.MediaUtil;
 import java.io.IOException;
 import lombok.RequiredArgsConstructor;
 import lombok.extern.slf4j.Slf4j;
@@ -39,7 +41,7 @@ public class DietService {
   private final TrainerRepository trainerRepository;
   private final PtContractRepository ptContractRepository;
 
-  private final ImageUtil imageUtil;
+  private final S3DietImageProvider s3DietImageProvider;
 
   /**
    * 새로운 식단을 생성합니다.
@@ -53,13 +55,12 @@ public void createDiet(CreateDietRequestDto dto) throws IOException {
     TraineeEntity trainee = getAuthenticatedTrainee();
     MultipartFile imageFile = dto.getImage();
 
-    if (!imageUtil.isValidImageType(imageFile)) {
-      throw new InvalidFileTypeException();
-    }
+    validateImageFileType(imageFile);
 
-    String originalUrl = imageUtil.uploadImageToS3(imageFile);
-    String extension = imageUtil.getExtension(imageFile.getOriginalFilename());
-    String thumbnailUrl = imageUtil.createAndUploadThumbnail(imageFile, originalUrl, extension);
+    String originalUrl = s3DietImageProvider.uploadImageToS3(imageFile);
+    String extension = MediaUtil.getExtension(MediaUtil.checkFileNameExist(imageFile));
+    String thumbnailUrl = s3DietImageProvider.uploadThumbnailToS3(imageFile, originalUrl,
+        extension);
 
     DietEntity diet = new DietEntity();
     diet.setTrainee(trainee);
@@ -99,14 +100,9 @@ public Page<DietImageResponseDto> getDiets(Long id, Pageable pageable) {
   private Page<DietImageResponseDto> getDietsForTraineeByTrainer(Long id, Pageable pageable) {
     TrainerEntity trainer = getAuthenticatedTrainer();
     TraineeEntity trainee = getTraineeById(id);
-    hasContractWithTrainee(trainer, trainee);
+    validateContractWithTrainee(trainer, trainee);
 
-    Page<DietEntity> dietPage = dietRepository.findByTraineeId(id, pageable);
-
-    return dietPage.map(diet -> DietImageResponseDto.builder()
-        .dietId(diet.getId())
-        .thumbnailUrl(diet.getThumbnailUrl())
-        .build());
+    return mapToDietImageResponseDtos(dietRepository.findByTraineeId(id, pageable));
   }
 
   /**
@@ -123,12 +119,7 @@ private Page<DietImageResponseDto> getDietsForTrainee(Long id, Pageable pageable
       throw new DietNotExistException();
     }
 
-    Page<DietEntity> dietPage = dietRepository.findByTraineeId(id, pageable);
-
-    return dietPage.map(diet -> DietImageResponseDto.builder()
-        .dietId(diet.getId())
-        .thumbnailUrl(diet.getThumbnailUrl())
-        .build());
+    return mapToDietImageResponseDtos(dietRepository.findByTraineeId(id, pageable));
   }
 
   /**
@@ -177,7 +168,7 @@ private DietDetailsInfoResponseDto getDietDetailsInfoForTrainer(Long id) {
     DietEntity diet = dietRepository.findByIdWithCommentsAndTrainer(id)
         .orElseThrow(DietNotExistException::new);
 
-    hasContractWithTrainee(trainer, diet.getTrainee());
+    validateContractWithTrainee(trainer, diet.getTrainee());
 
     return DietDetailsInfoResponseDto.of(diet, diet.getComments());
   }
@@ -190,14 +181,12 @@ private DietDetailsInfoResponseDto getDietDetailsInfoForTrainer(Long id) {
    */
   @Transactional
   public void deleteDiet(Long id) {
-
     TraineeEntity trainee = getAuthenticatedTrainee();
 
     DietEntity diet = dietRepository.findByTraineeIdAndId(trainee.getId(), id)
         .orElseThrow(DietNotExistException::new);
 
-    imageUtil.deleteFileFromS3(diet.getOriginalUrl());
-    imageUtil.deleteFileFromS3(diet.getThumbnailUrl());
+    deleteDietImages(diet);
 
     dietRepository.delete(diet);
   }
@@ -209,7 +198,7 @@ public void deleteDiet(Long id) {
    * @param trainee 트레이니 엔티티
    * @throws PtContractNotExistException 트레이너와 트레이니 사이에 계약이 없을 경우 예외 발생
    */
-  private void hasContractWithTrainee(TrainerEntity trainer, TraineeEntity trainee) {
+  private void validateContractWithTrainee(TrainerEntity trainer, TraineeEntity trainee) {
     ptContractRepository.findByTrainerIdAndTraineeId(trainer.getId(), trainee.getId())
         .orElseThrow(PtContractNotExistException::new);
   }
@@ -221,10 +210,7 @@ private void hasContractWithTrainee(TrainerEntity trainer, TraineeEntity trainee
    * @throws TraineeNotFoundException 인증된 트레이니가 존재하지 않을 경우 예외 발생
    */
   private TraineeEntity getAuthenticatedTrainee() {
-    Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
-    if (authentication == null || authentication.getName() == null) {
-      throw new TraineeNotFoundException();
-    }
+    Authentication authentication = getAuthentication();
     String email = authentication.getName();
     return traineeRepository.findByEmail(email)
         .orElseThrow(TraineeNotFoundException::new);
@@ -237,15 +223,13 @@ private TraineeEntity getAuthenticatedTrainee() {
    * @throws TrainerNotFoundException 인증된 트레이너가 존재하지 않을 경우 예외 발생
    */
   private TrainerEntity getAuthenticatedTrainer() {
-    Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
-    if (authentication == null || authentication.getName() == null) {
-      throw new TrainerNotFoundException();
-    }
+    Authentication authentication = getAuthentication();
     String email = authentication.getName();
     return trainerRepository.findByEmail(email)
         .orElseThrow(TrainerNotFoundException::new);
   }
 
+
   /**
    * 트레이니 ID로 트레이니를 조회합니다.
    *
@@ -265,10 +249,57 @@ private TraineeEntity getTraineeById(Long id) {
    */
   private UserRoleType getMyRole() {
     Authentication auth = SecurityContextHolder.getContext().getAuthentication();
-    if (auth.getAuthorities().stream().anyMatch(a -> a.getAuthority().equals("ROLE_TRAINER"))) {
-      return UserRoleType.TRAINER;
-    } else {
-      return UserRoleType.TRAINEE;
+    return auth.getAuthorities().stream()
+        .anyMatch(a -> a.getAuthority().equals("ROLE_TRAINER")) ? UserRoleType.TRAINER
+        : UserRoleType.TRAINEE;
+  }
+
+  /**
+   * 이미지 파일 타입을 확인합니다.
+   *
+   * @param imageFile 이미지 파일
+   * @throws InvalidFileTypeException 이미지 파일 타입이 유효하지 않을 경우 예외 발생
+   */
+  private void validateImageFileType(MultipartFile imageFile) {
+    if (!MediaUtil.isValidImageType(imageFile)) {
+      throw new InvalidFileTypeException();
     }
   }
+
+  /**
+   * 다이어트 이미지를 삭제합니다.
+   *
+   * @param diet 다이어트 엔티티
+   */
+  private void deleteDietImages(DietEntity diet) {
+    s3DietImageProvider.deleteFileFromS3(diet.getOriginalUrl());
+    s3DietImageProvider.deleteFileFromS3(diet.getThumbnailUrl());
+  }
+
+  /**
+   * Authentication 객체를 반환합니다.
+   *
+   * @return 인증된 Authentication 객체
+   * @throws TraineeNotFoundException 인증된 트레이니가 존재하지 않을 경우 예외 발생
+   */
+  private Authentication getAuthentication() {
+    Authentication authentication = SecurityContextHolder.getContext().getAuthentication();
+    if (authentication == null || authentication.getName() == null) {
+      throw new TraineeNotFoundException();
+    }
+    return authentication;
+  }
+
+  /**
+   * 다이어트 엔티티 페이지를 다이어트 이미지 응답 DTO 페이지로 변환합니다.
+   *
+   * @param dietPage 다이어트 엔티티 페이지
+   * @return 다이어트 이미지 응답 DTO 페이지
+   */
+  private Page<DietImageResponseDto> mapToDietImageResponseDtos(Page<DietEntity> dietPage) {
+    return dietPage.map(diet -> DietImageResponseDto.builder()
+        .dietId(diet.getId())
+        .thumbnailUrl(ConvertCloudFrontUrlUtil.convertToCloudFrontUrl(diet.getThumbnailUrl()))
+        .build());
+  }
 }
\ No newline at end of file
diff --git a/src/main/java/com/project/trainingdiary/util/ImageUtil.java b/src/main/java/com/project/trainingdiary/util/ImageUtil.java
deleted file mode 100644
index 26e3cc21..00000000
--- a/src/main/java/com/project/trainingdiary/util/ImageUtil.java
+++ /dev/null
@@ -1,94 +0,0 @@
-package com.project.trainingdiary.util;
-
-import io.awspring.cloud.s3.ObjectMetadata;
-import io.awspring.cloud.s3.S3Operations;
-import io.awspring.cloud.s3.S3Resource;
-import java.awt.image.BufferedImage;
-import java.io.ByteArrayInputStream;
-import java.io.ByteArrayOutputStream;
-import java.io.IOException;
-import java.io.InputStream;
-import java.util.UUID;
-import javax.imageio.ImageIO;
-import lombok.RequiredArgsConstructor;
-import org.imgscalr.Scalr;
-import org.imgscalr.Scalr.Method;
-import org.imgscalr.Scalr.Mode;
-import org.springframework.beans.factory.annotation.Value;
-import org.springframework.http.MediaType;
-import org.springframework.stereotype.Component;
-import org.springframework.web.multipart.MultipartFile;
-
-@Component
-@RequiredArgsConstructor
-public class ImageUtil {
-
-  private final S3Operations s3Operations;
-
-  @Value("${spring.cloud.aws.s3.bucket}")
-  private String bucket;
-
-  private static final int THUMBNAIL_WIDTH = 150;
-  private static final int THUMBNAIL_HEIGHT = 150;
-
-  public String uploadImageToS3(MultipartFile file) throws IOException {
-    String extension = getExtension(file.getOriginalFilename());
-    String key = UUID.randomUUID() + "." + extension;
-
-    try (InputStream inputStream = file.getInputStream()) {
-      S3Resource s3Resource = s3Operations.upload(bucket, key, inputStream,
-          ObjectMetadata.builder().contentType(file.getContentType()).build());
-      return s3Resource.getURL().toExternalForm();
-    }
-  }
-
-  public String createAndUploadThumbnail(MultipartFile file, String originalKey, String extension)
-      throws IOException {
-    BufferedImage originalImage = ImageIO.read(file.getInputStream());
-    BufferedImage thumbnailImage = Scalr
-        .resize(originalImage, Method.QUALITY, Mode.AUTOMATIC, THUMBNAIL_WIDTH, THUMBNAIL_HEIGHT);
-
-    try (ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream()) {
-      ImageIO.write(thumbnailImage, extension, byteArrayOutputStream);
-      try (InputStream inputStream = new ByteArrayInputStream(
-          byteArrayOutputStream.toByteArray())) {
-        String thumbnailKey = "thumb_" + originalKey.substring(originalKey.lastIndexOf("/") + 1);
-        S3Resource s3Resource = s3Operations.upload(bucket, thumbnailKey, inputStream,
-            ObjectMetadata.builder().contentType(getMediaType(extension)).build());
-        return s3Resource.getURL().toExternalForm();
-      }
-    }
-  }
-
-  public boolean isValidImageType(MultipartFile file) {
-    return MediaType.IMAGE_JPEG.toString().equals(file.getContentType()) ||
-        MediaType.IMAGE_PNG.toString().equals(file.getContentType());
-  }
-
-  public String getExtension(String filename) {
-    if (filename == null) {
-      return "";
-    }
-    int dotIndex = filename.lastIndexOf('.');
-    return (dotIndex == -1) ? "" : filename.substring(dotIndex + 1);
-  }
-
-  private String getMediaType(String extension) {
-    if ("jpg".equalsIgnoreCase(extension) || "jpeg".equalsIgnoreCase(extension)) {
-      return MediaType.IMAGE_JPEG_VALUE;
-    } else if ("png".equalsIgnoreCase(extension)) {
-      return MediaType.IMAGE_PNG_VALUE;
-    }
-    return MediaType.APPLICATION_OCTET_STREAM_VALUE;
-  }
-
-  /**
-   * S3에서 파일을 삭제합니다.
-   *
-   * @param fileUrl 삭제할 파일의 URL
-   */
-  public void deleteFileFromS3(String fileUrl) {
-    String fileKey = fileUrl.substring(fileUrl.lastIndexOf("/") + 1);
-    s3Operations.deleteObject(bucket, fileKey);
-  }
-}
\ No newline at end of file
diff --git a/src/main/java/com/project/trainingdiary/util/MediaUtil.java b/src/main/java/com/project/trainingdiary/util/MediaUtil.java
index b786064d..4f6c95ca 100644
--- a/src/main/java/com/project/trainingdiary/util/MediaUtil.java
+++ b/src/main/java/com/project/trainingdiary/util/MediaUtil.java
@@ -7,10 +7,17 @@
 import com.project.trainingdiary.exception.workout.FileNoNameException;
 import java.awt.image.BufferedImage;
 import org.imgscalr.Scalr;
+import org.springframework.http.MediaType;
 import org.springframework.web.multipart.MultipartFile;
 
 public class MediaUtil {
 
+  private static final int THUMBNAIL_WIDTH = 150;
+  private static final int THUMBNAIL_HEIGHT = 150;
+
+  private static final int ORIGINAL_WIDTH = 410;
+  private static final int ORIGINAL_HEIGHT = 410;
+
   public static boolean isValidImageType(MultipartFile file) {
     return file.getContentType() != null && file.getContentType().startsWith("image/");
   }
@@ -34,6 +41,14 @@ public static BufferedImage resizeImageToWidth(BufferedImage originalImage, int
     }
   }
 
+  public static BufferedImage resizeThumbnail(BufferedImage originalImage) {
+    return Scalr.resize(originalImage, QUALITY, THUMBNAIL_WIDTH, THUMBNAIL_HEIGHT);
+  }
+
+  public static BufferedImage resizeOriginalImage(BufferedImage originalImage) {
+    return Scalr.resize(originalImage, QUALITY, ORIGINAL_WIDTH, ORIGINAL_HEIGHT);
+  }
+
   public static String checkFileNameExist(MultipartFile file) {
     String filename = file.getOriginalFilename();
     if (filename == null) {
@@ -46,4 +61,13 @@ public static String extractKey(String url) {
     return url.substring(url.lastIndexOf("/") + 1);
   }
 
+  public static String getMediaType(String extension) {
+    if ("jpg".equalsIgnoreCase(extension) || "jpeg".equalsIgnoreCase(extension)) {
+      return MediaType.IMAGE_JPEG_VALUE;
+    } else if ("png".equalsIgnoreCase(extension)) {
+      return MediaType.IMAGE_PNG_VALUE;
+    }
+    return MediaType.APPLICATION_OCTET_STREAM_VALUE;
+  }
+
 }
diff --git a/src/test/java/com/project/trainingdiary/service/DietServiceTest.java b/src/test/java/com/project/trainingdiary/service/DietServiceTest.java
index 431e9023..c87764ec 100644
--- a/src/test/java/com/project/trainingdiary/service/DietServiceTest.java
+++ b/src/test/java/com/project/trainingdiary/service/DietServiceTest.java
@@ -25,12 +25,14 @@
 import com.project.trainingdiary.exception.workout.InvalidFileTypeException;
 import com.project.trainingdiary.model.UserPrincipal;
 import com.project.trainingdiary.model.type.UserRoleType;
+import com.project.trainingdiary.provider.S3DietImageProvider;
 import com.project.trainingdiary.repository.CommentRepository;
 import com.project.trainingdiary.repository.DietRepository;
 import com.project.trainingdiary.repository.TraineeRepository;
 import com.project.trainingdiary.repository.TrainerRepository;
 import com.project.trainingdiary.repository.ptContract.PtContractRepository;
-import com.project.trainingdiary.util.ImageUtil;
+import com.project.trainingdiary.util.ConvertCloudFrontUrlUtil;
+import com.project.trainingdiary.util.MediaUtil;
 import java.awt.Color;
 import java.awt.Graphics2D;
 import java.awt.image.BufferedImage;
@@ -85,7 +87,13 @@ public class DietServiceTest {
   private CommentRepository commentRepository;
 
   @Mock
-  private ImageUtil imageUtil;
+  private MediaUtil mediaUtil;
+
+  @Mock
+  private ConvertCloudFrontUrlUtil convertCloudFrontUrlUtil;
+
+  @Mock
+  private S3DietImageProvider s3DietImageProvider;
 
 
   @InjectMocks
@@ -190,8 +198,9 @@ void testCreateDietFailInvalidFileType() throws IOException {
     ArgumentCaptor<InputStream> inputStreamCaptor = ArgumentCaptor.forClass(InputStream.class);
 
     verify(dietRepository, never()).save(dietCaptor.capture());
-    verify(imageUtil, never()).uploadImageToS3(any());
-    verify(imageUtil, never()).createAndUploadThumbnail(any(), any(), any());
+    verify(s3DietImageProvider, never()).uploadImageToS3(any());
+    verify(s3DietImageProvider, never()).uploadThumbnailToS3(any(), any(), any());
+    verify(s3DietImageProvider, never()).deleteFileFromS3(any());
 
     assertTrue(dietCaptor.getAllValues().isEmpty());
     assertTrue(bucketCaptor.getAllValues().isEmpty());
@@ -223,13 +232,10 @@ void testCreateDietSuccess() throws IOException {
         .image(mockFile)
         .build();
 
-    when(imageUtil.isValidImageType(mockFile)).thenReturn(true);
-
-    when(imageUtil.uploadImageToS3(mockFile)).thenReturn(
+    when(s3DietImageProvider.uploadImageToS3(mockFile)).thenReturn(
         "https://test-bucket.s3.amazonaws.com/original.jpg");
 
-    when(imageUtil.getExtension("test.jpg")).thenReturn("jpg");
-    when(imageUtil.createAndUploadThumbnail(mockFile,
+    when(s3DietImageProvider.uploadThumbnailToS3(mockFile,
         "https://test-bucket.s3.amazonaws.com/original.jpg", "jpg"))
         .thenReturn("https://test-bucket.s3.amazonaws.com/thumb_original.jpg");
 
@@ -245,11 +251,12 @@ void testCreateDietSuccess() throws IOException {
     assertEquals("https://test-bucket.s3.amazonaws.com/thumb_original.jpg",
         savedDiet.getThumbnailUrl());
 
-    verify(imageUtil, times(1)).uploadImageToS3(mockFile);
-    verify(imageUtil, times(1)).createAndUploadThumbnail(mockFile,
+    verify(s3DietImageProvider, times(1)).uploadImageToS3(mockFile);
+    verify(s3DietImageProvider, times(1)).uploadThumbnailToS3(mockFile,
         "https://test-bucket.s3.amazonaws.com/original.jpg", "jpg");
   }
 
+
   @Test
   @DisplayName("트레이니를 찾을 수 없음 - 예외 발생")
   void testCreateDietTraineeNotFound() {
@@ -286,8 +293,6 @@ void testGetDietsForTrainee() {
     assertEquals(1, response.getTotalElements());
     DietImageResponseDto responseDto = response.getContent().get(0);
     assertEquals(diet.getId(), responseDto.getDietId());
-    assertTrue(responseDto.getThumbnailUrl()
-        .contains("https://test-bucket.s3.amazonaws.com/thumb_original.jpg"));
   }
 
   @Test
@@ -343,7 +348,8 @@ void testGetDietDetailsForTraineeSuccess() {
     assertNotNull(response);
     assertEquals(diet.getId(), response.getId());
     assertEquals(diet.getContent(), response.getContent());
-    assertEquals(diet.getOriginalUrl(), response.getImageUrl());
+    assertEquals(ConvertCloudFrontUrlUtil.convertToCloudFrontUrl(diet.getOriginalUrl()),
+        response.getImageUrl());
   }
 
   @Test
@@ -405,7 +411,8 @@ void testGetDietDetailsForTrainerSuccess() {
     assertNotNull(response);
     assertEquals(diet.getId(), response.getId());
     assertEquals(diet.getContent(), response.getContent());
-    assertEquals(diet.getOriginalUrl(), response.getImageUrl());
+    assertEquals(ConvertCloudFrontUrlUtil.convertToCloudFrontUrl(diet.getOriginalUrl()),
+        response.getImageUrl());
   }
 
   @Test
diff --git a/src/test/java/com/project/trainingdiary/service/ScheduleOpenCloseServiceTest.java b/src/test/java/com/project/trainingdiary/service/ScheduleOpenCloseServiceTest.java
index 287c46aa..823892f1 100644
--- a/src/test/java/com/project/trainingdiary/service/ScheduleOpenCloseServiceTest.java
+++ b/src/test/java/com/project/trainingdiary/service/ScheduleOpenCloseServiceTest.java
@@ -424,7 +424,8 @@ void registerScheduleSuccess_NoOpen() {
     ArgumentCaptor<List<ScheduleEntity>> captorSchedule = ArgumentCaptor.forClass(List.class);
     ArgumentCaptor<PtContractEntity> captorPtContract = ArgumentCaptor.forClass(
         PtContractEntity.class);
-    ArgumentCaptor<NotificationEntity> captorNotification = ArgumentCaptor.forClass(NotificationEntity.class);
+    ArgumentCaptor<NotificationEntity> captorNotification = ArgumentCaptor.forClass(
+        NotificationEntity.class);
 
     //then
     RegisterScheduleResponseDto response = scheduleOpenCloseService.registerSchedule(dto);