The present invention provides an optical angle sensor capable of detecting a wide range of angles with high resolution, having no scale, and specifying a reference angle. The optical angle sensor includes a light source for irradiating light, a reflection means for rotating around a predetermined axis as a measurement axis and reflecting the light irradiated from the light source, a light receiving means for receiving the light irradiated from the light source, and a calculation means for calculating the light received by the light receiving means as a signal. The light receiving means receives the light irradiated from the light source through the reflection means. The calculation means includes a specifying means for specifying the reference angle based on the light received by the light receiving means, and an angle calculating unit for calculating an absolute angle based on the light received by the light receiving means and the reference angle specified by the specifying means.