An image forming apparatus is provided. The image forming apparatus includes a photosensitive body unit including a photosensitive body, at least one developing unit including a developing roller that is configured to contact the photosensitive body or to be separated from the photosensitive body, and a press device to press the developing unit in order to contact or separate the photosensitive body and the developing roller to/from each other. The press device includes at least one lever configured to rotate about an end portion thereof and press the developing unit by rotation, and at least one cam configured to allow the lever to rotate by rotation thereof. Since the lever gradually rotates by rotation of the cam, force applied to the developing unit through the lever is also gradually and smoothly increased or decreased. Accordingly, shock, which may occur by rough movement of the developing unit, is remarkably reduced.