PURPOSE: To surely separate an electrifying roller or a transfer roller from a photoreceptor when an image forming device is not used, without using a solenoid.

CONSTITUTION: A cam 16, which pushes up the shaft 21 of an electrifying roller 3 and moves the roller against the pressure of a spring 12 to separate it from the photoreceptor 2 when rotation is transmitted in the opposite direction to the arrow A, is attached to the rotary support shaft 11 of the photoreceptor 2 via a one-way bearing 18, which transmits the rotation to the cam 16 only when the photoreceptor 2 rotates in the opposite direction to the direction of the rotation (shown by an arrow A) used in image formation. After the image formation is finished, the photoreceptor 2 is rotated reversely a prescribed amount, thereby, turning the cam 16 and separating the electrifying roller 3 from the photoreceptor 2. In the case where the device has the transfer roller, it can also be separated from the photoreceptor at the same time, by changing the shape of the cam.