An antenna device includes a feeder coil connected to a feeder circuit, a first conductor surface including a first slit that extends in a direction toward an outer edge and a second conductor surface including a second slit that extends in a direction toward an outer edge. The feeder coil is arranged at a position that is superposed with the first slit when viewed in plan, the feeder coil and the first conductor surface are magnetically coupled with each other, the first conductor surface and the second conductor surface are magnetically coupled with each other and the first slit and the second slit are arranged at positions so as to be partially superposed with each other when viewed in plan. At least a portion of the first slit is superposed with a portion of the second conductor surface other than the second slit when viewed in plan, and at least portion of the second slit is superposed with a portion of the first conductor surface other than the first slit when viewed in plan.