An antenna comprises a ground plate which is planar; a first power feed
element which is disposed separately from the ground plate by a
prescribed distance and which is formed in a prescribed shape; a first
parasitic element which is planar and which is formed in a prescribed
shape; a first shortcircuit part which electrically connects the first
parasitic element and the ground plate; and a power feed part which is
electrically connected with the first power feed element, wherein the
first power feed element and the first parasitic element are disposed in
parallel in part with each other, and the first power feed element and
the first parasitic element have multiple resonances by electro magnetic
coupling.