To provide an adjusting mechanism adjusting height of an apparatus, particularly, correcting deviation of the height positions between the discharge port of an image forming apparatus and the feed port of a post-processing device with simple structure.

By movably engaging the support shaft 32 of a wheel 31 in a slot 51 formed at a lower part of the side wall of the apparatus, the wheel 31 is attached so as to partially project from the base of the apparatus. Then, a stopper member 6 with three recessed parts 61a, 61b and 61c having a different distance from the center of rotation is turnably attached to the upper part of the slot 51. The position of the upper end of the support shaft 32 movable in the slot 51 is regulated by the recessed parts of the stopper member 6. By turning the stopper member 6 to select the recessed part to abut on the support shaft 32, the projecting amount of the wheel 31 from the base of the apparatus is adjusted and then the height of the apparatus is adjusted.