Abstract: There is provided a windmill-shaped loop antenna including: a dielectric substrate; a first radiation unit disposed on a top surface of the dielectric substrate and including a metal pattern having loop pieces; a second radiation unit disposed at a bottom surface of the dielectric substrate and including a metal pattern having loop pieces arranged not to face the loop pieces of the first radiation unit; and a plurality of identical transmission line from a center of the top and bottom surfaces of the dielectric substrate to the first and second radiation units, which form windmill-shaped metal pattern with the first and second radiation unit.