A vehicle-mounted antenna device includes a base, a board, a circuit section, and a housing. The base is mountable on a roof of a vehicle. The board has an antenna element section and is stood on the base. The circuit section is implemented on the board and serves as at least part of a wireless communication circuit electrically connected to the antenna element section. The housing is made of a resin material and forms a projection of an outer shape of the vehicle. The board and the circuit section are located in space formed by the base and the housing. A heat transfer path having a thermal conductivity higher than that of air is formed between the circuit section and the housing without passing the base.