support plate 2 thereby keeping the body 1 stable also when the body 1 is raised the manual sheet feed plate 18 is kept at its projecting end above the projecting surface of each rubber cusuion 44 thereby being kept a space from the floor where the sheet discharge tray 53 is housed by its own weight into the body 1 in addition the toner 10 within the toner hopper 15 and the developer 12 in the developing unit 11 are biased at the reverse side with respect to the photosensitive drum 4 in a case where the apparatus body 1 is intended to be inclined by 90 u00b0 reversely from its lengthwise upright standing posture to a horizontal operation posture the original support plate 2 need only be moved toward the side wall reverse to the lock member 71 mounted side wall so that the bent portion of lock member 71 disengages from the recess 72 at the cover 3 and the lock member 71 is retracted from the upper surface of the body 1 by the tension spring 74 thereby making the original support plate 2 slidable in reciprocation along the upper surface of body 1 incidentally when the original support plate 2 is set to slide initially toward the opposite side to the lock member 71 the person can immediately operate the apparatus without releasing the lock member 71 in other words when he starts copying operation after the body 1 is placed on a horizontal base the original support plate 2 at first slides away from the lock member 71 in the direction of releasing it thereby being automatically unlocked as abovementioned hence the lock member 71 cannot hinder the sliding of original support plate.