PURPOSE: To prevent the deformation of a developing sleeve which can not be recovered and to restrain the occurrence of a defective image by providing a means for forming alternating electric field, and a switching means which turns on/off an alternating electric field forming means so that the developing sleeve and an electrostatic latent image carrier are tightly adhered with each other or their tight adhersion is released.
CONSTITUTION: A photosensitive drum 100 is an organic photosensitive body and driven in a specified direction, and the driving roller 10 of a developing device 1 is made of foamed silicone and driven in the specified direction. As the roller 10 rotates, the sleeve 11 rotates in the same direction by frictional force between the roller 10 and the sleeve 11. The voltage of an AC power source Va and that of a DC power source Vb are superposed and impressed on the developing sleeve 11 through the roller 10 and an on/off operating switch SW. When the device is not used, the developing sleeve 11 and the photosensitive drum 100 are set in a state where they are slightly in contact or non-contact. In the case of developing operation, AC voltage is impressed by the power sources Va and Vb so that attracting force by which the sleeve 11 and the drum 100 are tightly adhered with each other is allowed to act, and the alternating electric field is formed.