An existing printer arranged to print data from a PC (personal computer) is used as the printer unit of a facsimile apparatus. The PC uses a printer driver dedicated to an existing printer (capable of performing the same processing as the printer unit of the facsimile apparatus) as a module, serving as application software for a facsimile-apparatus control unit, for printing the data from the PC. When printing data from the PC, a command uniquely directed to the facsimile apparatus is added to the printing data generated by the PC's printer driver, and the resultant data is transmitted to the facsimile apparatus. Upon receipt of the transmitted data, the facsimile apparatus removes the added command, thus restoring the printing data generated by the printer driver, and transmits the restored data to the printer unit to perform printing. It is thus possible to use the printer unit and the printer driver which utilize existing printers, and to cause the facsimile apparatus to wait in a state of receiving a common command system.