A developing device, which can inhibit the increase of the rate of uncharged toner caused by long hours of operation and develop an excellent image, and a process cartridge and an image forming apparatus that use such a developing device. A developing sleeve is rotary driven, and has, as magnetic field generating means that is fixedly disposed within the developing sleeve, a magnet roll composed of a plurality of stationary magnets. The magnet roll has five magnetic poles, P1 (south pole), P2 (north pole), P3 (north pole), P4 (south pole) and P5 (north pole), which are arranged in the direction of rotation of the developing sleeve in this order starting from a developing position that is a region facing a photoreceptor. On the periphery of the developing sleeve, there is disposed blade-shaped developer accumulation means, which is attached to a developer container at a position between a doctor blade and a stirring section and in the vicinity of the stirring section, with a predetermined space between the developing sleeve and the developer accumulation means.