Hello @yoji sato ,
welcome to this moderated Azure community forum.
The maximum message size for the Azure IoT Hub is 256KB.
It seems you experience a lower amount than documented.
Please create a support ticket because Microsoft is able to check the logs of the specific resources.
If the response helped, do "Accept Answer". If it doesn't work, please let us know the progress. All community members with similar issues will benefit by doing so. Your contribution is highly appreciated.