Abstract: Provided is an antenna device whose characteristics are enhanced (radio waves are efficiently emitted from an extended antenna) without need to place a communication unit that wirelessly communicates with the outside of a vehicle in close proximity to a loop structure of the vehicle, thus allowing a high flexibility of installation of the communication unit. An antenna device mounted on a vehicle includes a communication unit configured to wirelessly communicate with an outside of the vehicle, and a metal bracket configured to serve also as an extended antenna, and the communication unit includes a housing and a substrate-accommodated in the housing and on which a pattern antenna is formed, the metal bracket includes a first part fixed to the housing and a second part fixed to the vehicle.