diff --git a/cerrors/cerrors.go b/cerrors/cerrors.go
index 63e2b22..9b2db0d 100644
--- a/cerrors/cerrors.go
+++ b/cerrors/cerrors.go
@@ -21,6 +21,7 @@ const (
 	UnavailableErr
 	ResourceExhaustedErr
 	Canceled
+	AlreadyExists
 )
 
 func (e ErrorCode) String() string {
@@ -45,6 +46,8 @@ func (e ErrorCode) String() string {
 		return "ResourceExhaustedErr"
 	case Canceled:
 		return "Canceled"
+	case AlreadyExists:
+		return "AlreadyExists"
 	default:
 		return "UnknownErr"
 	}
@@ -75,7 +78,8 @@ func defaultErrorLevel(code ErrorCode) ErrorLevel {
 		ParameterErr,
 		ResourceExhaustedErr,
 		FailedPreconditionErr,
-		Canceled:
+		Canceled,
+		AlreadyExists:
 		return ErrorLevelWarn
 	case UnknownErr,
 		UnimplementedErr,
diff --git a/cerrors/cerrors_test.go b/cerrors/cerrors_test.go
index 75a2126..b7eccf4 100644
--- a/cerrors/cerrors_test.go
+++ b/cerrors/cerrors_test.go
@@ -236,6 +236,13 @@ func Test_ErrorCode_String(t *testing.T) {
 			},
 			want: "Canceled",
 		},
+		{
+			name: "AlreadyExists",
+			args: args{
+				code: AlreadyExists,
+			},
+			want: "AlreadyExists",
+		},
 		{
 			name: "不正値",
 			args: args{