PURPOSE: To eliminate the need to use a new driving roller and improve maintenance by allowing a driving and a driven roller to be replaced with each other, and using the driven roller as a driving roller when the driving roller wears away to be disabled to use.

CONSTITUTION: The photosensitive body belt driving device consists of the driving roller 20 and driven rollers 21 and 21, etc., around which a photosensitive body belt 1 is wound around together with the driving roller. Those rollers 20W 22 use their support shafts 20a, 21a, 22a, etc., in common to use by replacing one another. The diameter of thr roller 21 is set larger than that of the roller 20, and the diameter of the driven roller 22 is set larger than that of the roller 21. When the roller 20 wears away in long-period use and should be replaced, the diameter of the roller 21 becomes equal to the diameter of the roller 20 before use. Similarly, the diameter of the roller 22 becomes equal to that of the roller 21 before use. Then, those rollers are only replaced.