To execute communication between each image forming device and a central control unit even without using dedicated data communication equipment or making all image forming devices have a remote communication function.

When a printer 4 is connected to a compound machine 5 having a FAX function (remote communication function) through a LAN 8 by a LAN I/F, communication between the machine 5 and a central control unit 10 is performed through a public line 30, and communication between the printer 4 and the unit 10 is performed through the LAN 8, the machine 5 and the line 30. Also, the personal computer 13 of the unit 10 converts data received from OA equipment including the FAX equipment 1 of a client destination, a copying machine 2, the printer 4 and each image forming device of the machine 5 into a common format.