PURPOSE: To prevent deterioration of performance of a photosensitive material due to frictional heat between a platen and a photosensitive body belt by cooling the platen forcibly by refrigerant.

CONSTITUTION: By pressing a copy start key, the photosensitive belt is driven by the controlling signal of a controlling section 26a and all processes of the device are driven. At the same time, as a driving circuit 27 is operated to drive a circulating device 24, heat absorbing medium is circulated to cool a platen 16. The heat absorbing medium is cooled in a heat exchanger 25 and flows into a cooling pipe 22 in the platen 16 through a pipe 23. Accordingly, frictional heat between the platen 16 and photosensitive belt can be absorbed at all times. Cold wind can be blown in place of the heat absorbing medium.