Developing device using two-component developer

In a developing device for visualizing an electrostatic latent image using two-component developer containing toner and magnetic carrier, excellent development will be performed and deterioration of the developer will be prevented. A developer carrier opposite to an image carrier having an electrostatic latent image formed thereon is prepared by forming a thin layer of aluminum with a thickness of 3 mu m or less on the peripheral surface of a roll-shaped member made of ferrite, and the surface roughness Rz of the peripheral surface of the foregoing ferrite roll is set to 50 mu m or less. N-poles and S-poles are alternately magnetized at a 50-to-250- mu m pitch along the peripheral surface of this ferrite roll. These magnetic poles can be magnetized to have uniform intensity because the peripheral surface of the roll has been smoothly finished, and a developer layer having only substantially one layer of the carrier uniformly attracted is formed on the peripheral surface. On the other hand, a magnetic recording layer is provided on a roll-shaped conductive substrate, and its surface may be finished so as to satisfy relation of Rz