To simplify the transmission and reception processing operations on a gate side and on a road and, at the same time, to reduce the cost.

A first device 11A on a gate 11 side is composed mainly of an interface 20, an amplifier 21, a modulator 22 constituting a modulating means 13, a semiconductor laser 23 constituting a light projecting means 14, a galvano- mirror 24 constituting a reflecting means 15, and a driver 26 and housed in a compact box. A second device 12A on a vehicle 12 side is composed mainly of a half mirror 40 and optical sensors 33 and 33 constituting a light receiving means 16, a semiconductor laser 23 constituting a light projecting means 14, a galvanomirror 40 constituting a reflecting means 15, a driver 26, an optical sensor 32 and the half-mirror 40 constituting the light emitting means 16, a demodulating means 17, and a displaying section 39 constituting a displaying means 19. Since the second device 12A also has such a size that the device 12A can be housed in a compact box, the cost of the devices 11 and 12 can be reduced.