An API counting process that sets a limit number for an API used by a client, and when an access token is issued in response to a request from an authority delegation destination and a request to verify the issued access token is received, manages an API usage limit number on a client-by-client basis in accordance with the usage limit number for each API set for the authority delegation destination, is executed. The API usage number is incremented (S5.2), compared with the usage limit number (S5.3), and the access token verification is considered to have failed in the case where the limit has been exceeded.