Patent ID: 8374528

Claim:
A developing device that houses a developing agent including carrier and toner, and that develops a latent image formed on an image carrier, comprising: at least one developing roller; a plurality of transport members which have a screw portion formed on a shaft portion, and which transport the developing agent housed within the device in a longitudinal direction, and form a circulation path; and a discharge aperture, formed in a wall of a transport path of one of the transport members, that discharges the developing agent outside the circulation path when a level of the developing agent transported by the one of the transport members exceeds a predetermined height, wherein the one of the transport members is disposed adjacent to the developing roller that supplies the developing agent and includes, in a part in the longitudinal direction, an area on which the screw portion is not formed, the discharge aperture is disposed opposite to the area on which the screw portion is not formed on the one of the transport members, and the length of the discharge aperture is formed smaller than that of the area in the longitudinal direction, and a length from an upstream end of the discharge aperture in the transportation direction of the developing agent to an upstream end of the area on which the screw portion is not formed, is greater than a length from a downstream end of the discharge aperture in the transportation direction of the developing agent to a downstream end of the area on which the screw portion is not formed.