Abstract: Disclosed is an image forming apparatus having moving means for moving a coupling gear between a coupling position where a drum side coupling portion and a main body side coupling portion are coupled to each other and a decoupling position where the drum side coupling portion and the main body side coupling portion are decoupled from each other. The moving means moves the coupling gear to the coupling position when forming a color image, and moves the coupling gear to the decoupling position when forming a monochrome image. The coupling gear has a main body side gear portion which meshes with the main body gear. The coupling gear is integrally molded with the main body side coupling portion and the main body side gear portion.