A rotary encoder includes a rotary shaft that may be manufactured easily and efficiently includes a rotating magnet with a mounting precision in which variance may not occur readily. A rotary shaft includes a rotary shaft main unit with a rotating magnet mounting part for mounting a rotating magnet and a ring-shaped rotating magnet that is formed integrally with this rotating magnet mounting part of the rotary shaft. In a method of manufacturing the rotary shaft, a ring-shaped rotating magnet is formed integrally with the rotary shaft mounting part of the rotary shaft main unit.