An object of the present invention is to provide a radio-on-fiber unit and a radio-on-fiber system which can transmit/receive signals at adequate rates especially, to/from a mobile device. A first aspect of the present invention relates to a radio-on-fiber unit (3) which includes an antenna array (1) and a light modulator array (2). The light modulator array (2) comprises antenna elements (5) and light modulators (7) that are connected with the respective antenna elements via electric circuits. The optical waveguide (13) is composed of linear optical waveguides (13) that are arranged along the light modulators (7) included in certain lines among the light modulators (7). The light modulator array (2) comprises reflection units (17) for connecting two adjacent linear optical waveguides with each other. Consequently, a signal light inputted to a light input unit (11) is outputted from a light output unit (15) via each linear optical waveguide (13).