PURPOSE: To make high-speed performance higher and make constitution simpler and smaller while maintaining the accuracy of a light polarizer by forming a rotary polyhedral mirror body with a metal material and forming the rotary polyhedral mirror body into one piece with a revolving shaft.

CONSTITUTION: A motor revolving shaft 1' with polyhedral mirror is supported at its both ends with ball bearings 11 and 12 a polyhedral mirror body part consisting of the plural mirror face parts C1'WC8' which are concentrical to the axial center and are parallel is formed into the same body as the revolving shaft 1', between said two end supports. The mirror face parts of this motor revolving shaft 1' with polyhedral mirror is worked to mirror surfaces with high accuracy mainly by a diamond turning method which is new metal surface working technique. In addition, with such constitution, the number of the mirror faces may be made from 8 to 12, whereby the high-speed performance may be made higher: moreover, the constitution of the supporting parts of the polyhedral mirror body is simplified and further the number of steps of polishing work may be decreased, whereby the working may be simplified.