PURPOSE: To stabilize quality of printing, use a photosensitive body effectively, and prolong the service life of a photosensitive drum by detecting the damage of the photosensitive body by a winding detector for printing paper sheet and winding the photosensitive body based on the detected signal.

CONSTITUTION: To facilitate the restoration of a winding paper sheet on a photo-sensitive body 16, a detector 11 is provided at the front of a charger 12 relative to the rotational direction of a photosensitive drum 15, the winding of the paper sheet is detected, and the photosensitive drum 15 is immediately stopped. The damage of the photosensitive body 16 is detected by the detector 11, and the photosensitive body 16 is wound based on the detected signal. Also the detector 11 comprises one light emitting element and two light receiving elements to detect both direct reflected light and diffused reflection angle. Thus the damage is compared with the set value of a slice level determined based on the quality of printing and the size of damage of the photosensitive body to detect the presence or absence of harmful damage on the photosensitive body.