diff --git a/rog/serializers.py b/rog/serializers.py
index b2d1fdd..57ab769 100755
--- a/rog/serializers.py
+++ b/rog/serializers.py
@@ -925,7 +925,7 @@ class MemberCreationSerializer(serializers.Serializer):
 
     firstname = serializers.CharField(required=False, allow_blank=True)
     lastname = serializers.CharField(required=False, allow_blank=True)
-    date_of_birth = serializers.DateField(required=False)
+    date_of_birth = serializers.DateField(required=False, allow_null=True)  # allow_null=True を追加
     female = serializers.BooleanField(required=False)