PURPOSE: To provide an optical scanner capable of reducing an adverse influence exerted on an image by the heat radiation of a motor and preventing the image from being deteriorated.

CONSTITUTION: This optical scanner 10 is constituted of a polygon mirror 32 having reflection surfaces 32a to 32h and formed to be rotatable, the motor 31 including a rotor 31b rotating the polygon mirror, a fixed part 31c rotating the rotor and a motor base 31d separating the rotor and the fixed part to be on front and back sides, an airtight chamber 13 housing the polygon mirror in an airtight state, and a housing 11 holding the motor base so that the polygon mirror may be housed in the airtight chamber and holding the motor so that the fixed part may be on the outside relatively to the airtight chamber and the movement of heat from the fixed part may be prevented. Thus, the image is prevented from being deteriorated by the heat radiation of the motor, so that the image is stably formed with a uniform laser beam.