The invention is to provide an image forming apparatus and an electrophotographic cartridge, which are free from problems of cleaning failure, filming, soiling, residual images (ghosts), fogging, density reduction, noise and the like and which can provide high-definition images even when a toner having a small particle size and having a high degree of circularity is used and even when a photoreceptor having a small outer diameter is used. An image forming apparatus comprising: an electrophotographic photoreceptor containing a conductive support and a photosensitive layer on the conductive support, a charging unit for charging the electrophotographic photoreceptor, an imagewise exposing unit for imagewise exposing the charged electrophotographic photoreceptor to form an electrostatic latent image thereon, a developing unit for developing the electrostatic latent image with a toner, and a transferring unit for transferring the toner from the electrophotographic photoreceptor to a receiving unit, wherein the outer diameter of the electrophotographic photoreceptor is 20 mm or less, the photosensitive layer contains a polyarylate resin, and the toner satisfies the specific requirements (1) and (2).