In a developing device having a developing zone where an image carrier and a
developer
carrier face each other, the developer carrier carrying a developer thereon moves
at a linear velocity of 150 mm/sec or above, but below 500 mm/sec. The amount of
the developer conveyed to the developing zone by the developer carrier is between
65 mg/cm2 and 95 mg/cm2. A magnetic flux generated on the
developer carrier in the developing zone by a magnetic pole has a flux density
having an attenuation ratio of 40% in the direction normal to the developer carrier.
The flux density in the direction normal to the developer carrier, as measured
on the surface of the developer carrier, is between 100 mT and 200 mT. Magnetic
grains, which constitute the developer together with toner grains, have a saturation
magnetization value of 4010-74 Wbm/kg or above,
but below 5010-74 Wbm/kg.
