An antenna device includes a substrate formed of a dielectric body or a magnetic body, first to third radiation conductors wound in spirals around outer circumferential surfaces of the substrate, a plurality of capacitance elements spread over the first radiation conductor and the second radiation conductor, and a high-frequency switch interposed between feed ends. The feed ends are selectively connected to a high-frequency circuit via the high-frequency switch connected to a tuner. Since the total length of the second and third radiation conductors connected in series with each other is longer than that of the first radiation conductor, the first radiation conductor is capable of resonating in a high band and the second and third radiation conductors are capable of resonating in a low band. By changing the capacitances of the variable capacitance elements from the tuner side, a resonant frequency can be changed within a selected frequency band.