Radar loss caused by a windshield having laminated glass in a vehicle is suppressed with a simple configuration. An antenna's radiation section is disposed inside the windshield of a vehicle having a plurality of layers. The radiation section not only radiates radio waves but also receives reflected waves of the radio waves from a target. A distance measurement information generation section is connected to the radiation section. The distance measurement information generation section measures a distance to the target on the basis of the radiated radio waves and the reflected waves from the target and generates distance measurement information.