[Problem] To provide a low-profile antenna device able to be inexpensively manufactured by reducing the number of structural components and the number of assembly steps and the like without impairing antenna performance. [Solution] The low-profile antenna device for a vehicle comprises a base plate 10, a circuit substrate 20, a base 30, a top load element 40, and a coil 50. The circuit substrate 20 is positioned on the base plate 10 to be parallel with the base plate 10. An amplifier circuit 21 is mounted on the front surface side of the circuit substrate 20, and a ground plate area 22 having a ground plate and a blank area 23 not having a ground plate are provided on the rear surface of the circuit substrate 20. The coil 50 is positioned on the front surface side of the circuit substrate 20 facing the blank area 23 of the circuit substrate 20. The coil 50 is positioned so as to be axially parallel with the circuit substrate 20, connected between the top load element 40 and the amplifier circuit 21, and adjusted so as to function as a resonance antenna.