diff --git a/src/main/java/es/princip/ringus/infra/storage/application/S3Service.java b/src/main/java/es/princip/ringus/infra/storage/application/S3Service.java
index 5fc8db8..65c7ea1 100644
--- a/src/main/java/es/princip/ringus/infra/storage/application/S3Service.java
+++ b/src/main/java/es/princip/ringus/infra/storage/application/S3Service.java
@@ -38,17 +38,22 @@ public class S3Service {
      * @return 업로드된 파일의 S3 URL
      */
     public String uploadFile(MultipartFile file, String folderPath, boolean isPublic) {
-        String fileName = UUID.randomUUID() + "_" + sanitizeFileName(file.getOriginalFilename());
+        // 파일명: UUID + 확장자만 추출
+        String extension = getExtension(file.getOriginalFilename());
+        String fileName = UUID.randomUUID() + (extension != null ? "." + extension : "");
         String s3Key = folderPath + "/" + fileName;
+
         try {
+            PutObjectRequest.Builder requestBuilder = PutObjectRequest.builder()
+                    .bucket(bucketName)
+                    .key(s3Key)
+                    .contentType(file.getContentType());
+
             s3Client.putObject(
-                    PutObjectRequest.builder()
-                            .bucket(bucketName)
-                            .key(s3Key)
-                            .contentType(file.getContentType())
-                            .build(),
+                    requestBuilder.build(),
                     RequestBody.fromInputStream(file.getInputStream(), file.getSize())
             );
+
         } catch (IOException e) {
             throw new RuntimeException("파일 입력 스트림을 읽지 못했습니다.", e);
         } catch (S3Exception e) {
@@ -97,4 +102,14 @@ public String generatePresignedUrl(String s3Key, Duration duration) {
             return presignedRequest.url().toString();
         }
     }
+
+    /**
+     * 파일 확장자 추출
+     */
+    private String getExtension(String fileName) {
+        if (fileName == null || !fileName.contains(".")) {
+            return null;
+        }
+        return fileName.substring(fileName.lastIndexOf('.') + 1);
+    }
 }
diff --git a/src/main/java/es/princip/ringus/infra/storage/application/StoragePortfolioService.java b/src/main/java/es/princip/ringus/infra/storage/application/StoragePortfolioService.java
index febed79..bed7c2b 100644
--- a/src/main/java/es/princip/ringus/infra/storage/application/StoragePortfolioService.java
+++ b/src/main/java/es/princip/ringus/infra/storage/application/StoragePortfolioService.java
@@ -21,7 +21,7 @@ public class StoragePortfolioService {
     @Transactional
     public String uploadMentorPortfolio(PortfolioUploadRequest request, Long memberId) {
         String folderPath = "portfolio/mentor/" + memberId;
-        String filePath = s3Service.uploadFile(request.file(), folderPath, false);
+        String filePath = s3Service.uploadFile(request.file(), folderPath, true);
 
         fileMemberRepository.save(request.toFileMemberEntity(filePath, memberId));
         return filePath;