Abstract: A developing magnet roller is provided on a developing frame, and a developing agent accommodating cartridge and a toner accommodating cartridge member are fitted detachably into the developing frame. The toner accommodating cartridge member is fitted detachably into the developing agent accommodating cartridge. A developing agent is recovered in the developing agent accommodating cartridge. The developing agent and the developing agent accommodating cartridge are exchanged together from a developing apparatus. The new developing agent accommodated in the exchanged new developing agent accommodating cartridge is circulated by the developing magnet roller. The exchange for the developing agent in the developing apparatus can be realized without the lowering of the developing performance.