The service does not provide a feature to bulk download multiple files, such as all of the files attached to a specific app. Files can only be downloaded one at a time.

As a workaround, it is possible to use an API to download attached files in bulk.

You can find information on APIs, including API manuals and sample code, on the following pages.

• Features of the Command Line Tool
• Bulk Download Attachment Files
• Two steps you need to perform when downloading files (Only available in Japanese)

If you have any questions about APIs, refer to the following page: 
Inquiring about APIs, customization, or extensions