A multi-resonant antenna device includes an antenna element and an LC parallel resonance circuit making the antenna element resonate in a plurality of frequency bands, and the LC parallel resonance circuit includes a T-type circuit or PI-type circuit including an inductance element, acting as a shunt element, and capacitance elements, which prevent the impedance from becoming infinite in a certain frequency band. In this way, a drop, that is, a notch portion, in the frequency characteristic causing deterioration of the gain can be eliminated.