To secure an appropriate light quantity made incident on a photoreceptor without increasing heat-generating quantity, space, weight and noise.

An illumination optical system 12 illuminating an original on a glass base 11 is arranged under the glass base 11, and a full speed scanning mirror 13 and a half speed scanning mirror 14 successively scanning all the area of an original are arranged to be integrally movable. A 1st image forming element 15 and a return mirror 16 are arranged in the advancing direction of the light reflected by the mirror 14, and a light amplifier means 18, a 2nd image forming element 19 and the photoreceptor 20 are arranged through a bending mirror 17 in the reflecting direction of the mirror 16. Since the light from the optical system 12 is optically amplified by the amplifier means 18 and formed an image on the photoreceptor 20, an appropriate light quantity made incident on the photoreceptor 20 is secured even when no output from the optical system 12, no brightness of the elements 15 and 19, nor the sensitivity of the photoreceptor 20 is improved.