An antenna device includes: an antenna element that transmits or receives wireless signals in a predetermined first frequency band and in a second frequency band higher in frequency than the first frequency band; a feeding terminal portion; a first bandwidth adjustment circuit that includes a first capacitor for widening a bandwidth of the first frequency band to a predetermined bandwidth, the capacitance of the first capacitor being set at a predetermined value in accordance with the predetermined bandwidth; and a second bandwidth adjustment circuit that includes second and third capacitors and a first inductor for widening a bandwidth of the first frequency band to the predetermined bandwidth, the capacitance of each of the second and third capacitors and the inductance of the first inductor being respectively set at predetermined values in accordance with the predetermined bandwidth.