A user information registration program 68 of PC3 obtains current time from a built-in timer. Sequentially, the user information registration program 68 extracts one registration destination information from a registration destination table. The user information registration program 68 calculates lease end time from the sum of lease period and registration response reception time in extracted registration destination information and compares the calculation result with current time. If current time exceeds lease end time, the user information registration program 68 adds the IP address of network scanner 2 relating to the current registration destination to a response table 120. Sequentially, user information of PC3 is registered to the network scanner 2 (registration destination). The user information registration program 68 registers new user information to all registration destinations (network scanners 2) registered in the registration destination table.