An image forming apparatus comprises a photoconductive unit having a waste toner outlet and a shutter for closing the waste toner outlet, a developing unit removably mounted to the photoconductive unit and having a waste toner storage for storing a waste toner discharged through the waste toner outlet, a main body for receiving and supporting the photoconductive unit and the developing unit and having a door, and an opening/closing member moving in association with an opening and closing movement of the door, thereby moving the shutter to a position for opening the waste toner outlet, wherein the shutter moves to the position for opening the waste toner outlet by mounting both the photoconductive unit and the developing unit and closing the door at the same time.