PURPOSE: To absorb and extrude a developer uniformly to form an image well, by providing a layer of a porous elastic member including foam parts on the axial circumferential face of a developing roller and coating the surface of the outside layer with a plating film including abrasive grains due to electroless plating.

CONSTITUTION: An elastic material 3 having open cell is provided around a shaft 2 of a developing roller 1, and the outside circumference of the roller 1 is coated with a net 4, and the surface of the net 4 is coated with a plating film including abrasive grains due to electroless plating. In a developing part where the developing roller 1 is pressed to a photosensitive drum 5, a developer 10 absorbed in the developing roller 1 is extruded; and the developing roller 1 separated from the developing part absorbs the developer 10 by its restoring force, and the internal developer is extruded when the developing roller 1 is pressed against a refresh roller 11, and the developing roller 1 absorbs a fresh developer in a bath 9. Thus, good pictures are always formed by the uniformity of developer absorption and extrusion on the contacting face and the wear resistance of the plating face.