Abstract: An apparatus for supplementing a toner into a toner hopper of a developing device using the toner including a toner supplementing container having a toner bottle having an opening, a shutter member movable between a close position in which the opening of the toner bottle is closed by the shutter member and an open position in which the opening of the toner bottle is not closed by the shutter member, and a shutter locking member for locking the shutter member into the close position; and a container fixing and locking mechanism arranged on the toner hopper and having a fixing member for fixing the toner supplementing container onto the toner hopper and a locking member which is movable into a locked position in which the shutter locking member is released to allow the movement of the shutter member into the open position and the toner supplementing container could not be removed from the toner hopper and an unlocked position in which the toner supplementing container can be removed from the toner hopper and th