From a printer, a print client previously acquires printer position information on the printer. For example, when trying to transmit print data to the printer, the print client generates print transmitting data by adding printer position information on the printer to the print data and transmits the print transmitting data. The printer which has received this print transmitting data prints the print data only when the printer position information contained in the print transmitting data coincides with printer position information at this point in time. Consequently, the security of the print transmitting data transmitted from the print client to the printer via a network is ensured.