PURPOSE: To execute control accurring no malfunction by providing a storage means storing the programs of each stage of an old version and a new version, on the master CPU of a controller.

CONSTITUTION: A copying machine main body 1 has the master CPU 2, a ROM 3, a RAM 4, and an operating load 5, and a peripheral equipment 6 has a slave CPU 7, a ROM 8, a RAM 9, and an operating load 10. A new program and the number of its version are stored in the ROM 3 of the copying machine main body 1 side whenever version-up is carried out. In other words, the master CPU 2 can control the slave CPU 7 in the stages of the version-up, etc., with the program stored in the ROM 3, as well. On the other hand, the programs of each stage are stored so as to correspond to the programs of any stages of the version-up in the slave CPU 7, as well, and simultaneously, the number of the versions of each program is stored. Then, this program is selected to carry out the control.