An antenna device includes first and second radiating elements, a first coil coupled to the first radiating element or a feeding circuit, a second coil coupled to the second radiating element and coupled to the first coil via an electromagnetic field, and an inductor. The first and second radiating elements are coupled to each other via an electric field. The harmonic resonant frequency of a resonance circuit defined by a transformer defined by the first coil and the second coil, the inductor, and the second radiating element exists within a communication frequency range. The harmonic resonant frequency is a (2n+1)th harmonic frequency, where n is an integer equal to or greater than 1.