A three-axis antenna having a first to a third antenna coils arranged so that directions of the maximum reception sensitivities are orthogonal to each other, the first to the third antenna coils comprising respectively: a planar coil being wound around the winding axis in circumferential direction and has an aperture; and a foil-type core inserted in the aperture; the foil-type core being arranged a plane to be in parallel to the plane of the first to the third coils.