PURPOSE: To improve development ability without disturbing a toner image formed on an image carrier.

CONSTITUTION: Two nip parts 33a and 33b are formed between the development sleeve 30 and the photosensitive drum 11 by forming a magnetic pattern, which has two projections with strong magnetic forces, by means of a development roller 24. A force with which developer 32 is carried is made weak by making the surface of the development sleeve 30 smooth, with a roughness of 0.5μm or less. In the upstream nip part 33a, the magnetic brush comes into soft contact with an electrostatic latent image on the photosensitive drum 11. In the downstream nip part 33b, an amount of accumulating developer 32 increases by a reduction in the carrying force of the development sleeve 30, therefore the area where the magnetic brush is in contact with the electrostatic latent image is made wide and the development ability improves.