In order to provide an antenna that is small and resonates at a plurality of frequencies, an antenna according to the present invention is provided with: a first conductor of a ring shape, having an air gap; a second conductor arranged inside the ring, with both ends of the second conductor connected to the first conductor, having a first gap; and a third conductor arranged in a region surrounded by a part not including the air gap out of the first conductor, and the second conductor, with both ends connected to the first conductor, having a second gap, and a value obtained by multiplying a length of an outer periphery of a region surrounded by a part including the air gap out of the first conductor, and the third conductor, by capacitance of the air gap is different from a value obtained by multiplying a length of an outer periphery of a region surrounded by the second conductor, the third conductor, and the first conductor, by capacitance of the first gap.