An optical position sensor provided with an input optical fiber (2), output optical fibers (3, 4), a flat light conductor (6) disposed on a substrate (1) and having a branched light conductor (14), a first columnar lens (11) adapted to transform the optical path of the light wave projected from the flat light conductor (6) and focus the light wave onto the surface to be detected, and a second columnar lens (12) adapted to transform the optical path of the light wave reflected off the surface to be detected and introduce the light wave into the flat light conductor (6). This configuration provides a small optical position sensor that has good detection characteristics even over long measurement distances.