An image forming apparatus includes a photosensitive body, an exposure unit, a pulse generating unit, a smoothing unit, a drive current generating unit, and a second emitting control unit. The exposure unit includes a light source for emitting a light beam, and causes the light beam emitted from the light source to perform scanning in a main scanning direction, thereby drawing a main scanning line on the photosensitive body. The second emitting control unit causes the light source to emit the light beam, in an APC period of automatically controlling the light quantity of the light beam, by causing the pulse generating unit to generate a pulse signal having a duty ratio of 100 percent, causing the smoothing unit to smooth the pulse signal thereby generating an analog signal, and causing the drive current generating unit to generate a drive current based on the analog signal.