A developing device of the present invention includes a photosensitive drum and a developing roller facing the drum. The developing roller accommodates a stationary magnet roller that forms on the surface of the developing roller a scoop-up pole for scooping up the developer stored in the developing device onto the developing roller and a release pole adjoining the scoop-up pole for causing part of the developer moved away from a developing zone to be released from the developing roller between it and the scoop-up pole. The scoop-up pole, which is of the same polarity as the release pole, is configured such that a position where the flux density thereof in the direction normal to the surface of the developing roller is maximum is located closer to the release pole than a position on the above surface corresponding to the center of a range in which the above flux density is halved.