A dielectric member 27 with a thickness of from 0.1&lgr; to 2&lgr; is disposed opposite to a patch plane 17 of a patch antenna 10A apart from the patch plane 17 by a distance of from 0.1&lgr;0 to 2&lgr;0, where &lgr;0 and &lgr; are the wavelengths of a radiated radio wave in free space and in the dielectric member, respectively. The dielectric constant of the dielectric member 27 may be lower in an outer portion thereof than a middle portion thereof. When the antenna is incorporated into the communication module, the dielectric member 27 is attached to the cover of the communication module.