diff --git a/src/main/java/com/kamco/cd/kamcoback/postgres/core/CommonCodeCoreService.java b/src/main/java/com/kamco/cd/kamcoback/postgres/core/CommonCodeCoreService.java
index b3541ed9..259b885c 100644
--- a/src/main/java/com/kamco/cd/kamcoback/postgres/core/CommonCodeCoreService.java
+++ b/src/main/java/com/kamco/cd/kamcoback/postgres/core/CommonCodeCoreService.java
@@ -43,7 +43,7 @@ public class CommonCodeCoreService
   @CacheEvict(value = "commonCodes", allEntries = true)
   public ResponseObj save(CommonCodeDto.AddReq req) {
 
-    String regex = "^([A-Z]+|[0-9]+|[A-Z0-9]+(_[A-Z0-9]+)+)$";
+    String regex = "^[A-Z0-9]+(_[A-Z0-9]+)*$";
     boolean isValid = req.getCode().matches(regex);
     if (!isValid) {
       return new ResponseObj(ApiResponseCode.CONFLICT, "공통코드에 영문 대문자, 숫자, 언더바(_)만 입력 가능합니다.");
@@ -76,9 +76,11 @@ public class CommonCodeCoreService
                           "parent id 를 찾을 수 없습니다. id : " + req.getParentId()));
 
       entity.addParent(parentCommonCodeEntity);
+    } else {
+      entity.addParent(null);
     }
-
     commonCodeRepository.save(entity).toDto();
+
     return new ResponseObj(ApiResponseCode.OK, "");
   }
 
@@ -202,7 +204,7 @@ public class CommonCodeCoreService
   public ResponseObj getCodeCheckDuplicate(Long parentId, String code) {
     Long existsCount = commonCodeRepository.findByParentIdCodeExists(parentId, code);
 
-    String regex = "^([A-Z]+|[0-9]+|[A-Z0-9]+(_[A-Z0-9]+)+)$";
+    String regex = "^[A-Z0-9]+(_[A-Z0-9]+)*$";
     boolean isValid = code.matches(regex);
     if (!isValid) {
       return new ResponseObj(ApiResponseCode.CONFLICT, "공통코드에 영문 대문자, 숫자, 언더바(_)만 입력 가능합니다.");
diff --git a/src/main/java/com/kamco/cd/kamcoback/postgres/repository/code/CommonCodeRepositoryImpl.java b/src/main/java/com/kamco/cd/kamcoback/postgres/repository/code/CommonCodeRepositoryImpl.java
index 2557240d..4298eedd 100644
--- a/src/main/java/com/kamco/cd/kamcoback/postgres/repository/code/CommonCodeRepositoryImpl.java
+++ b/src/main/java/com/kamco/cd/kamcoback/postgres/repository/code/CommonCodeRepositoryImpl.java
@@ -4,6 +4,7 @@ import static com.kamco.cd.kamcoback.postgres.entity.QCommonCodeEntity.commonCod
 
 import com.kamco.cd.kamcoback.postgres.entity.CommonCodeEntity;
 import com.kamco.cd.kamcoback.postgres.entity.QCommonCodeEntity;
+import com.querydsl.core.types.dsl.BooleanExpression;
 import com.querydsl.jpa.impl.JPAQueryFactory;
 import java.util.List;
 import java.util.Optional;
@@ -106,10 +107,16 @@ public class CommonCodeRepositoryImpl implements CommonCodeRepositoryCustom {
     return queryFactory
         .select(commonCodeEntity.code.count())
         .from(commonCodeEntity)
-        .where(commonCodeEntity.parent.id.eq(parentId), commonCodeEntity.code.eq(code))
+        .where(conditionParentId(parentId), commonCodeEntity.code.eq(code))
         .fetchOne();
   }
 
+  private BooleanExpression conditionParentId(Long parentId) {
+    return parentId == null
+        ? commonCodeEntity.parent.id.isNull()
+        : commonCodeEntity.parent.id.eq(parentId);
+  }
+
   private List<CommonCodeEntity> findAllByIds(Set<Long> ids) {
     return queryFactory
         .selectFrom(commonCodeEntity)