An optical signal receiver receives an optical signal superimposed on illumination light from an illumination apparatus which repetitively transmits as the optical signal a frame including predetermined information and a preamble indicating the start of the frame. Further, the optical signal receiver includes a light receiving unit configured to receive the optical signal, and a controller configured to control the light receiving unit based on the optical signal received by the light receiving unit such that the optical signal receiver operates in either one of an intermittent reception mode of intermittently receiving the optical signal and a continuous reception mode of continuously receiving the optical signal.