An image forming apparatus includes a frame, a photosensitive drum, an endless belt disposed above the photosensitive drum, and a pressing member. The photosensitive drum includes a drum body and a flange portion that is provided on one end portion of the drum body. The flange portion has a contacted portion and a pressed portion. The pressing member presses the pressed portion upward to permit the photosensitive drum to be in contact with the endless belt. The frame has a positioning portion disposed above the pressing member and above the photosensitive drum. The positioning portion is configured to be in contact with the contacted portion and to position the photosensitive drum when the pressing member presses the pressed portion. The pressed portion is disposed farther from the drum body in an axial direction of the photosensitive drum than the contacted portion.