<p>This invention relates to an image forming apparatus in which a cleaning device (40) is arranged above a photosensitive drum close thereto. The image forming apparatus has an image processing unit provided with the photosensitive drum. The photosensitive drum (3) is constructed such that a gear portion (31a) formed in a flange member at one axial end of the photosensitive drum has a diameter not greater than an outer diameter of the photosensitive drum. The image processing unit is constructed such that a driving force from the image forming apparatus is transmitted to the photosensitive drum via the gear portion (31a) formed in the one flange member to rotate the photosensitive drum (3) and is transmitted to at least one of image processor means via a gear portion (32a) formed in a flange member at the opposite axial end of the photosensitive drum. With this arrangement, a poor image formation due to a blocking phenomenon resulting from long stay of toner residues can be prevented and downsizing of the image forming apparatus is realized. <IMAGE></p>
