Patent ID: 8346134

Claim:
A developing device comprising: a developer retaining member that develops a latent image formed on an image retaining member using developer containing toner; at least three transport screws that are provided in a casing and rotate about a respective rotational axis for agitating and transporting the developer, said at least three transport screws including, a supply transport screw that supplies the developer to the developer retaining member, a receiving transport screw that receives the developer from the developer retaining member, wherein the rotational axes of the supply transport screw and the receiving transport screw are mutually parallel in relation to the image retaining member, and an agitating transport screw that receives the developer from the receiving transport screw, agitates the developer and transports the developer to the supply transport screw; a supply port that receives new carrier into the casing; a discharge port and discharge device that discharge part of the developer housed in the casing to an outside of the developing device; and a developer transport amount regulation part provided on a downstream side from the discharge port in a direction of transport of the agitating transport screw that decreases a volume of part of a space between an interior wall of the casing and the agitating transport screw.