To provide an antenna system where the directivity of a plane antenna is enhanced for both of radiation and incidence of a radio wave and to provide an automatic train controller mounted with the antenna system.

The antenna system consists of a plane antenna 10 that emits or receives a radio wave at a microwave band and a lens antenna 20 made of a dielectric material and placed on the plane antenna. The plane antenna 10 is formed on an insulation board 11 and they are contained in a vessel consisting of a box 30 and an upper cover 40. Preferably, the lens antenna 20 is formed to be a convex lens or a concaved lens by interposing a dielectric material between a curved face 21 swollen outward in the radio wave radiation direction or concaved in the direction of an aperture and a plane 22 opposed to the curved face 21. For example, the antenna system is built in a ground element of an automatic train controller and placed on a crosstie in a track and opposed the on-vehicle element in a passing train to emit a communication radio wave thereto, or the antenna system may be built in the on-vehicle element to receive a communication radio wave.