PURPOSE: To reduce thermal influence and the size of its external shape, by arranging a laser beam generator and a polygon mirror driver at a side opposite to a fixation part around a photoconductive receptor, and providing one fixed mirror and exposing the surface of the photoconductive receptor to polarized light.

CONSTITUTION: A laser beam 7 from the laser generator is projected on a polygon mirror 18 and its angle of reflection varies; and the reflected beam reaches the exposed surface 6 through an F-O lens 19, fixed mirror 20, and cylindrical lens 21 to form a charge latent image on the surface of the photoconductive and light-sensitive drum 4. The charge latent image is developed by a developing device 8 into a toner image, which is transferred to recording paper by an electrostatic transferring device 10 and fixed securely by the fixation part 11, thereby discharging the paper. Consequently, the thermal influence of the fixation part is eliminated to prevent deterioration in efficiency on an optical path, so only one fixed mirror is limited to be used and the exposed surface 6 is positioned on the photosensitive drum surface on he side where the fixation part is arranged so that the beam is reflected at an acute angle for preventing a decrease in reflectivity; reliability such as life and stability is improved and the external size L is reduced.