An image forming apparatus includes a photosensitive drum that rotates in a predetermined direction, an LED head that exposes the photosensitive drum, a drum contact surface that contacts against the outer peripheral surface of the photosensitive drum, and a head contact surface that contacts the LED head. Further, the image forming apparatus includes a spacer for regulating a distance between the photosensitive drum and the LED head, and a coil spring for pressing the LED head toward the spacer. The LED head has an engagement hole to engage the spacer. The spacer has a protrusion that engages with the engagement hole and regulates movement of the LED head in a predetermined direction.