A process controlling unit included in a multifunction-device controller sends an acquired ID number and a request for identifying the user corresponding to the ID number, to a controller server. The controller server searches a user management file for user information corresponding to the ID number. The controller server sends, to the multifunction-device controller, information representing that user verification is successfully made when user information is acquired. Upon reception of such information, the process controlling unit permits the verified user to operate a copier making copies of documents. Upon completion of the copying operation, the process controlling unit acquires information representing the number of copies made by the user. Then, the process controlling unit creates usage information of the copier, and sends the created usage information to the controller server. The controller server stores the received usage information into a usage-information management file.