<p>A polygon mirror (10), comprising a mounting part (12) and a plurality of reflecting surfaces (14). The mounting part (12) is installed on a rotating body (30) having a supporting surface (32b). The mounting part (12) is formed in a polygonal plate shape. The plurality of reflecting surfaces (14) are formed integrally with the mounting part (12), and disposed around the rotating body (30) so as to surround the rotating body (30). A plurality of projected parts (18) in contact with the supporting surface (32b) of the rotating body (30) are disposed on one surface of the mounting part (12).</p>
