PURPOSE: To realize an electrophotographic printer which has a both-side image- forming function, is miniaturized and enhanses speed and makes print output information coincide on the front and back surfaces in a vertical relation.

CONSTITUTION: An image forming device is equipped with: a photosensitive drum 22, with a layer of a photoreceptor 21 on its periphery, which is cylindrical and rotates normally and reversely in its circumferential direction; electrifying means 23A and 23B for uniformly electrifying the surface of the photoreceptor 21; an exposure means 24 for forming arm electrostatic latent image on the surface of the photoreceptor 21; developing means 25A and 25B for attaching developer T to the electrostatic latent image formed on the surface of the photoreceptor 21; a transfer means 26 for transferring the developer T, attached to the surface of the photoreceptor 21, to a recording medium P; and cleaning means 27A and 27B for removing the charges and developer remaining on the surface of the photoreceptor 21.