A developing device includes a first screw that supplies a developer to a developing roller while agitating/conveying the developer in a first direction, and a screw that collects residual developer from the developing roller, agitates/conveys the residual developer in a second direction opposite to the first direction, and delivers the residual developer to the first screw. Between two points that a magnetic flux density in a normal direction of a magnetic field formed in a developer separating magnetic pole in the developing roller become substantially zero, a point at a downstream side in a rotating direction of the developing roller is formed at an upstream side to a developing roller rotating direction, than a line joining the center of the developing roller and the center of the second screw.