PURPOSE: To facilitate assembling operation of a photosensitive rotor, stably earth it, and prevent vibration of the photosensitive rotor so as to print in high quality, by providing an earth member in contact with one end part of the photosensitive rotor and pushing the rotor in one direction along the axis.

CONSTITUTION: A photosensitive rotor 3 is earthed with an earth member 51 contacted with the end part 3a. Consequently, a connecting member to electrically communicate the photosensitive rotor 3 to a shafi in customary case is unnecessary to facilitate assembling operation. At performing printing operation, a motor 31 is driven to rotate an output rotor shaft 34. In this case, because a rotor 36 and the like are arranged between the bearing 35 of the motor 31 and the photosensitive rotor 3, even if lubricating oil is dispersed from the bearing 35, the oil is intercepted with the rotor 36 and the like not to reach the photosensitive rotor 3. The rotor 3 is pushed in the arrow mark E direction with a spring 39, and vibration and rolling of the rotor 3 can be prevented. Hereby, an image of high quality is formed.