A position measuring system including a laser light source for radiating a laser beam, an optical lens system for generating an interference pattern on the basis of the laser beam having passed through different optical paths, a detector for detecting the interference pattern, and an arithmetic unit for calculating the position of at least one of the light source and the detector on the basis of a detection signal issued from the detector. For example, a spherical lens can be used as the optical lens system. In this case, the interference pattern is formed on the basis of spherical aberration of the lens. Alternatively, a multifocal lens may be used as the optical lens system.