To obtain an optical scanner, where the light reflection surface of a counter mirror having a specified angle opposite to the surface of a movable mirror can be positioned and arranged accurately, and to provide a mechanism realizing high-quality image recording by correcting the bend of a scanning line, caused by multiple reflections.

In a mirror unit 1 arranged in the optical scanner, the movable mirror 3 is held on a movable mirror base plate 2, so as to reflect irradiating light several times with the counter mirror 10. The mirror 10 is formed through crystal anisotropic etching using two Si substrates 11 and 12 which have different crystal surface orientation. By forming inclined surfaces 14 and so on as the light reflecting surface, the angle of the inclined surfaces of two substrates can be formed exactly. Then, the reflection of the light beam and the light irradiation of a photoreceptor drum are performed via a prism arranged at the upper part.