IMAGE FORMING DEVICE

PURPOSE:To control an image forming process by a detecting value for the potential on the surface of a photosensitive body at a developing position and to always maintain stable picture quality by detecting said potential on a different position separated from a developing device. CONSTITUTION:An electrostatic charger 3, an image exposing means 4, a developing device 5, a transfer charger based on a 2nd charge applying means 6, etc., are arranged on the surface 2 of the photosensitive body in an electrophotographic copying device, a destaticizing lamp 12 is arranged on the position H of an angle beta on the upstream side of the means 6 and a photosensitive body surface potential measuring means 7 is arranged on the position D of an angle alpha on the downstream side. The 2nd exposing means based on a 2nd mirror 15 or the like so that an angle gamma from the means 6 is equal to an angle formed between the charger 3 and the exposing means 4. The potential on the surface of the photosensitive body at the developing position is detected on a position different from the developing device 5 and the image forming process is controlled by using the detecting value, so that always stable picture quality can be maintained.