To provide an antenna device for determining a link state of communication by controlling a tilt angle of an antenna element.

The antenna device comprises: a first transmission/reception antenna 3 including an antenna element 17 which is installed on a top surface of a vehicle and is tiltable, an antenna control unit 16 for controlling a tilt of the antenna element 17, and angle detection means 18 for detecting a tilt angle of the antenna element 17; and determination means 14 which determines the tilt angle of the antenna element 17 and a link state between the first transmission/reception antenna 3 and a second transmission/reception antenna 10 by transmitting/receiving identification signals between the first transmission/reception antenna 3 and the second transmission/reception antenna 10. When the determination means 14 determines that the antenna element 17 is tilted and the link state is not established, the antenna control unit 16 controls the antenna element 17 so that the tilt angle of the antenna element 17 is close to that in an upright state or is that in the upright state.