PURPOSE: To shorten a setting-up time and to attain the loading of a developing device only in the normal operating state of a developing device body by providing a stopper for preventing the developing device body from being inserted into a mounting pat under the fitting state of an aperture part closing cover to the developing device body on the cover.

CONSTITUTION: Due to the cover 65 is fitted to the developing device body in the free state of the developing device 9 which is not loaded into the mounting part, the aperture part 41 of the developing device body is closed and rotary roller 33 is prevented from rotation. Insertion preventing stoppers 75, 75 are protrusively provided to both the end parts of the cover body 67, and if the developing device is tried to be inserted into the mounting part under the covered state, the stoppers 75, 75 are engaged with the aperture edge part of the aperture part of a copying device body to interrupt the insertion. Said constitution make it possible to shorten the setting-up time and to load the developing device body only in the normal operation state of the uncovered developing device body.