An image forming apparatus for recognizing compatibility of an image forming process unit to be removably mounted at a given position within a main body of the apparatus, includes an engaging member mounting portion arranged to mount a recognition engaging member thereon, and a projecting member mounting portion arranged to mount thereon a recognition projecting member engageable with a recessed portion provided in the recognition engaging member. The projecting member mounting portion and the recognition engaging member mounting portion are respectively capable of mounting the recognition projecting member and recognition engaging member in two or more mounting states. The recognition projecting member and the recognition engaging member are mounted so as to be capable of being engaged with each other in the two or more mounting states so as to achieve compatibility recognition.