An antenna device attachable to a bottom surface of a resin or glass body of a vehicle, the antenna device includes: an antenna element that has a receiver for receiving radio waves; a circuit board that has a circuit surface having a circuit formed thereon to amplify signals inputted from the antenna element; a shield cover that covers the circuit surface of the circuit board to shield the circuit from interference waves and that is grounded; a coaxial cable that is inserted into the shield cover, that supplies a driving power to the circuit formed on the circuit board, that connects the circuit to a GND, and that outputs signals from the circuit; and a metallic bracket that has a lateral wall surrounding a lateral side of the antenna element and a bottom wall supporting a bottom of the antenna element.