An image forming apparatus has a first body capable of containing a movable photosensitive member therein and having first optics for applying, in a first mode, image information light obtained in the first body to the photosensitive member and forming an image on the photosensitive member, and a second body connected to the first body and having second optics for directing, in a second mode, an image information light obtained in the second body to the first body and forming an image on the photosensitive member in the first body. The width of the image formation area with respect to a direction orthogonal to the direction of movement of the photosensitive member is smaller in the second mode than in the first mode.