An image forming apparatus is disclosed including at least a plurality of image bearing members a plurality of image forming units each including plural image forming members for operating image forming steps onto each of the image bearing members, and a further image bearing member, which are held collectively on an image bearing member holding component. image forming unit holding component and second image bearing member holding component, respectively. By further providing a contact/detach mechanism adapted to detaching movements, within said image forming apparatus, of the image bearing member holding component and the second image bearing member holding component in relation to the image forming unit holding component, the mechanism is greatly simplified with relatively simple and less expensive construction of the mechanism disclosed herein, through eliminating plural contact/detach mechanisms separately provided for the noted holding components and also providing one integrating power sources for use in driving plural units in common. As a result, the previously known disadvantage in image forming apparatus such as contact residue images which are unduly caused by continual contact of the photoreceptors to image forming units and intermediate transfer belt can be obviated, as an example.