A developing device forms an image by developing an electrostatic latent image on a photoreceptor rotating about a rotation axis. The developing device includes a housing having an opening opposite the photoreceptor, a developing sleeve disposed inside the housing, a magnetic body disposed in a central portion of the developing sleeve and not in no-magnet portions thereof at both sides of the central portion, and seal members supported by the housing. Each of the seal members shields either one of portions of the photoreceptor that are located opposite the no-magnet portions and is in surface contact with either one of end portions of the photoreceptor farther from a center of the photoreceptor than the no-magnet portions. Each of the seal members includes, at an end thereof closer to the center of the photoreceptor than the other end thereof, a non-contact portion that is not in contact with the photoreceptor.