An image forming apparatus includes a housing, a photosensitive drum, a cleaning member, a driving transmission portion, and a movement mechanism. The photosensitive drum is rotatably supported by the housing about a first shaft portion. The driving transmission portion transmits a rotation driving force to the photosensitive drum. The movement mechanism reciprocates the photosensitive drum in an axial direction. The movement mechanism includes a first rotation gear, a second rotation gear, a first intermediate gear, and a second intermediate gear. The first rotation gear integrally rotates with the photosensitive drum. The second rotation gear has teeth different in number from teeth of the first rotation gear and rotates with a predetermined speed difference relative to the first rotation gear. The first and second intermediate gears are a pair of rotation gears rotatable about a second shaft portion parallel to the first shaft portion.