Patent ID: 7236726

Claim:
A developer cartridge comprising: a casing having a first inner space serving as a developer accommodating chamber that accommodates a developer and a second inner space serving as a developing chamber in communication with the developer accommodating chamber; an agitator disposed in the developer accommodating chamber and having a shaft portion that extends in an axial direction and that is rotatably supported in the casing, the agitator being rotatable about the shaft portion; a developing roller disposed in the developing chamber and rotatably supported in the casing, wherein the casing is formed with a developer opening located at a position closer to the developing chamber than the shaft portion is, the casing including a pair of side walls that have shaft bearing portions for supporting both axial ends of the shaft portion, wherein the developer opening is formed in one of the pair of side walls, and a gear mechanism that transmits a driving force to the developing roller and the agitator is disposed on an outer surface of an other of the pair of side walls, located opposite to the one of the pair of side walls in which the developer opening is formed.