PURPOSE: To prevent toner from existing on the surface of a developing roller exposed at outside of a developing device in an inoperative state.

CONSTITUTION: The developing roller 161 is constituted in such a manner that an electrostatic actuator member composed of a stator 166 composed of an insulator and plural driving electrodes 164 buried in the stator 166 is provided on a base roller 165 which can not be rotated. A prescribed voltage is applied to plural driving electrodes 164 by a power unit not shown by the figure, to generate driving force and carry the toner. It is constituted so that the voltage applied from the power unit can be changed over to obtain either of two applying methods in which a toner carrying direction is reversed each other, with a signal from a control part. A toner layer thinning blade 181 freely attached/ detached by a solenoid 180 is provided on the periphery of the roller. After a developing operation is completed, the toner carrying direction is changed over so as to be reverse to that at the time of developing, in a state where the blade 181 is moved to a retreating position, to recover the toner from the surface of the exposing part of the roller.