A developer cartridge for supplying a toner-containing developer, including a developer containing portion; a developer recovery portion, disposed at one end of the developer containing portion in a longitudinal direction; a supply port that supplies the developer from the developer containing portion to the developing unit; a recovery port through which used developer supplied from the developing unit passes to the developer recovery portion; and an opening and closing member, coupled to the outer circumferential of the developer containing portion and the developer recovery portion, that opens or closes the supply port and the recovery port. The developer containing portion has first and second end portions, the first end portion being more slender than the second end portion and linked to the developer recovery portion, wherein a tapered portion is provided between the first end portion and the second end portion.