PURPOSE: To detect the position of reflecting body having a simple structure without contacting and at high speed.

CONSTITUTION: While light from a semiconductor laser 10 is projected over a specific area at a broadening angle, the returned light from a reflecting body 35 placed in the irradiated area is condensed on a point of an optical position detecting element 50 through a condensing lens 40, and its output is subject to processing by a positional signal processing circuit 60 in order to detect the azimuth angle of the body 35. Since only the light from the body 35 is condensed at this time, only the light in a specific polarized direction can be selected by a polarizing beam splitter 20 and a one-fourth wavelength plate 30, and only the light with a specific wavelength be also selected by a monochromatic filter 41.