An antenna device includes: a feeding element having a feedpoint that a signal in a first frequency band and a signal in a second frequency band lower than the first frequency band are supplied to; a high-band element connected to the feeding element, the high-band element resonating with the signal in the first frequency band; a low-band element connected to the feeding element, the low-band element resonating with the signal in the second frequency band; an auxiliary element capacitively coupled to the low-band element at an open end of the low-band element; a ground member grounded; and a switch switching a conductive state and a non-conductive state between the ground member and the auxiliary element.