In a system made up of a plurality of devices such as a copier, an RDF, and a sorter, there is provided in each device a communication control device for providing communication between devices such that communication between devices can be performed independently of the device control unit inherent to that device. The communication control device includes data storage for storing device control data which can be accessed at random by a device control unit, access storage for storing access data indicating that the data storage is accessed, and a communication device for transmitting and receiving data stored in data storage. A synchronization storage device sets synchronization data indicating that the device control unit has set all the data to be transmitted in the data storage and synchronizes the device control unit and each communication control device on the basis of the synchronization data. Each communication control device further includes a protocol control device for controlling the communication device and the data storage such that any data stored in the data storage is read out and is transmitted and such that the data received by the communication device is stored at a predetermined in data storage means. In addition, the protocol control device controls the access storage device and the synchronization storage device.