An image forming apparatus is provided, including a housing, a drum cartridge, a developing cartridge, a drawer movable between an inner position and an outer position and a lock member provided on the drawer and movable between a lock position at which the lock member locks the drum cartridge to the drawer, and a release position at which a lock between the drum cartridge and the drawer is released. The lock member includes an operation portion for moving the lock member between the lock position and the release position. The developing cartridge includes a cover member that covers at least a portion of the operation portion in a state in which the drum cartridge is mounted to the drawer, and the developing cartridge is mounted to the drum cartridge.