PURPOSE: To achieve high resolution through a simple optical structure and at low cost in an optical scanner for use in linear beam scanning in a laser printer, a POS scanner and photometry, etc.

CONSTITUTION: An optical structure for varying the focal length of a spot image to be linearly scanned is provided in front of a polarizing portion 16 for linearly scanning on an image-focusing surface the spot image formed by condensing of a beam of light from a light source. The optical structure includes a first lens 11 for converting divergent light from a semiconductor laser 10 into a beam, an optical path separating optical element 12 such as a half mirror and a polarizing beam splitter(PBS) for separating light from the first lens 11, a second lens 13 for focusing one of the rays of light separated by the optical path separating optical element 12, and a reflecting portion 1-4 which can be displaced in the direction of the optical axis, used for reflecting convergent light from the second lens 13 so that the light passes through the second lens 13 and the optical path separating optical element 12 and enters the polarizing portion 16.