An image forming apparatus includes a main assembly and a cartridge attached to the main assembly in an attaching direction. The main assembly includes a movable member movable between first and second positions and having first and second engaging portions to engage with first and second protrusions on the cartridge, and an urging member urging the movable member from the second position to the first position. The first engaging portion has a surface-to-be-abutted, a first surface-to-be-supported, and a recessed surface, and the second engaging portion has a regulating surface and a second surface-to-be-supported.