A developer cartridge is constituted to be mounted attachably and detachably in a directional orthogonal to a rotating shaft of a developing unit main body and the developer cartridge has a developer containing portion and a developer recovery portion for recovering used developer from the developing unit. A supply port opens to supply the developer from the developer containing portion and a recovery port opens in the developer recovery portion to recover used and recovered developer. A supplying opening portion is formed in a shutter member at a position corresponding to the supply port and a recovering portion is formed in the shutter member at a position corresponding to the recovery port. The shutter member opens and closes both the supply port and the recovery port. A handle for operating the shutter member is configured so that it is contained in the rotating outer peripheral surface of the developing unit main body when the supply port and the recovery port are opened and so that it projects toward the outside of the rotating outer peripheral surface of the developing unit main body when the supply port and the recovery port are closed. The handle is also used to mount the developer cartridge on the developer unit main body.