An image forming apparatus includes a cover pivotable on a body to close an opening at a closed position and open the opening at an open position, first and second replacement units having photosensitive drums, an optical print head pivotable in one direction, a spring, and a stopper. The spring applies, to the optical print head, a force for allowing the optical print head to pivot toward the one direction so that a movement of the optical print head with a pivotal movement of the cover from the open position to the closed position is prevented from being inhibited by the first developing cartridge. The optical print head, having the force applied the optical print head by the spring, so that movement of the optical print head with pivotal movement of the cover from the open to the closed position is prevented from being inhibited by the second developing cartridge.