To solve the problem that a user needs to prepare a specific application or adds a specific plug-in to a browser so as to download and use a file and the problem that a file needs to be converted when uploaded.

On a file conversion server, a conversion module is prepared which can convert the format of an object file to be converted, and a conversion module is provided even from a module providing server when necessary. While those conversion modules are used, the format of the object file to be converted is converted to the format of a file that the user desires. Then the conversion is paid for. The user who is provided with this service need not perform troublesome file format converting operation.