In accordance with a replacing mechanism of the present invention, a toner cartridge is replaced from a main body of an image forming apparatus by performing, in a substantially same timing, an operation of closing a toner pouring opening with a cover by a levering action; and an operation of displacing the toner cartridge from the main body of the image forming apparatus to an operator side, the toner cartridge being provided with a flange portion. The toner cartridge cannot be pulled out unless the toner pouring opening is fully closed by the shutter member.