Patent ID: 7899373

Claim:
A developing device using a magnetic mono-component developing agent, comprising: a rotary sleeve that accommodates a stationary magnet; and a toner layer thickness regulating member that regulates a thickness of a toner layer formed on the rotary sleeve, wherein the toner layer thickness regulating member includes: a blade formed of a plate-like member made of a magnetic material; and a magnet attached to the blade on a side upstream in a rotation direction of the rotary sleeve, wherein the magnet is disposed in such a manner that a direction of a magnetic field generated in a portion of the magnet on a side of the rotary sleeve is almost in parallel with the rotation direction of the rotary sleeve, and wherein the blade is disposed in a direction perpendicular to the rotation direction of the rotary sleeve; the magnet is a plate-like magnet to be disposed in parallel with a plane direction of the blade; and the plate-like magnet has a magnetization direction perpendicular to the plane direction of the blade.