An image forming device includes an electrostatic latent image carrier which carries a latent image, a main frame which supports the latent image carrier, and a developing unit which is inserted removably in the main frame. The developing unit includes a developer carrier which supplies a developer to the electrostatic latent image carrier and a replenish chamber which replenishes the developer to the developer carrier. The image forming device also includes an operating unit to press or not press the developing unit by sliding a pressing body provided on the main frame, a manual operation unit provided on the operating unit and set at an operational position and a standby position, and a protrusion formed along an operational direction of the manual operation unit on a side surface of the developing unit located to the manual operation unit when the developing unit is inserted. When the manual operation unit is set at the operational position, the developing unit makes contact with the protrusion and is inserted.