A polygon mirror that can be manufactured at low cost and high productivity and a method of manufacturing the same, a polygon mirror that can be manufactured at low cost and presents little variations in reflectance in a wide range of angles of incident, an optical scanner and electrophotographic equipment that are less expensive and compact is provided. The polygon mirror has a single layer film formed of a substance having an index of reflection of 1.45 or below on the reflecting surface. The method of manufacturing the prism shaped polygon mirror having a film on the reflecting surface comprises a step of application for applying a solution containing a substance for forming a film on the reflecting surface, and a step of forming a coated film of the solution on the reflecting surface by rotating the polygon mirror, and the solution is applied only in the area of which the distance from the axis of rotation of the polygon mirror is at least Ri in the application step, where Ri is the minimum distance between the reflecting surface and the axis of rotation. The polygon mirror preferably has a film having the distribution of film thickness on the reflecting surface. Such a polygon mirror is included in the optical scanner and electrophotographic equipment.