diff --git a/prothsync/src/main/java/com/prothsync/prothsync/service/BlockService.java b/prothsync/src/main/java/com/prothsync/prothsync/service/BlockService.java
index cfb5e65..d7ed853 100644
--- a/prothsync/src/main/java/com/prothsync/prothsync/service/BlockService.java
+++ b/prothsync/src/main/java/com/prothsync/prothsync/service/BlockService.java
@@ -34,6 +34,10 @@ public class BlockService {
 
     @Transactional
     public BlockResponseDTO block(Long blockerId, Long blockedId) {
+        if (blockerId.equals(blockedId)) {
+            throw new BusinessException(BlockErrorCode.CANNOT_BLOCK_SELF);
+        }
+
         findUserOrThrow(blockerId);
         findUserOrThrow(blockedId);