PURPOSE: To execute easily attaching and detaching operations by providing an attaching and detaching lever which is engaged to a developing device cover for forming a part of a cover of a copying machine body and an engaging pin of the body side, and also intermits an electric connection of a power source for supplying an electric power to the copying machine body.

CONSTITUTION: A developing cover 2a is made in a shape of one body by plastic, and a hopper cover 3 and an attaching and detaching lever 4 are provided on its upper face part and the side face part, respectively. The tip of the attaching and detaching lever 4 is provided so as to be connected to a supporting shaft 7, and also a hook 5 is provided so as to be connected to one end of this supporting shaft 7. Also, this hook 5 is constituted so as to be engaged to an engaging pin 6 provided on the body side. That is to say, when the attaching and detaching lever 4 is moved in the direction of an arrow B, the hook 5 moves in the direction as indicated with an arrow C by using the supporting shaft 7 as a supporting point, and the engagement of the engaging pin 6 and the hook 5 is released. Also, this device is constituted so that an electric connection of a power source for supplying an electric power to a copying machine body 1 is cut off at the same time when the hook 5 turns in the direction as indicated with the arrow C.