PURPOSE: To prevent a reduction in printing density and a density unevenness by periodically discharging a toner on a development sleeve to prevent an abnormal rise in charged quantity of the toner.

CONSTITUTION: A modulated laser beam obtained by modulating a laser beam outputted from a laser light source 3 by a video signal is wrote and scanned in a point A on a photosensitive drum 1, after charged by a primary charger 2. A control part 15 and a laser light source driving circuit 14 continually light the laser light source 3 to form a solid black electrostatic image during a fixed time until the video signal of the second page is started after the modulation by the video signal of the first page is ended. According to the rotation of the drum 1, the solid black electrostatic image reaching the position of a development sleeve 4 is developed in the same manner as a conventional electrostatic image. After modulation by the video signals on and after the second page, the same operation as in the first page is repeated. As a large quantity of a toner on the sleeve 4 is evenly adhered to the drum 1 every page, thus, an abnormal rise in charged quantity of the toner can be prevented, and a reduction in density and a density unevenness can be prevented.