PURPOSE: To prevent erroneous loading of a tonr cartridge by providing the top of each toner cartridge with a detection piece corresponding to the kind of the toner, and providing the top body back with a switch for detecting the detection piece.

CONSTITUTION: The top of a toner cartridge supported in a developing unit is provided with detection pieces 13 and 14 corresponding to the color of the accommodated toner and a detection piece 14 for effecting a check as to whether there is a amounted toner cartridge. Color detection switches 16W18 and a cartridge detection switch 19 are provided at positions corresponding to the detection pieces 13W15 on the back of the top of a copier body 2. When a cartridge 12 is replaced and the copier body is then closed, the loading of the cartridge and the color of the toner can be displayed on a panel. It is thus possible to prevent erroneous loading of a toner cartridge.