Abstract: There is disclosed an optical measuring apparatus including a light scanning section for converting a light beam from a first light source to a parallel scanning light beam, a focussing section including a first focussing lens for focussing the parallel scanning light beam, an electric signal generating section for converting a focussed light to an electric signal, a measuring reference signal generating section and an electric signal processing section.The light scanning light section comprises a first mirror and a second mirror, each of which is rotated synchronously. The measuring reference comprises a transparent scale which is rotated in synchronism with the first and second mirrors, a light source, a second focussing lens and a second photoelectric conversion element. The electric signal processing section processes the electric signal from the electric signal generating section based on the measuring reference signal.