A feeding radiation electrode and a non-feeding radiation electrode are provided extending from a front side surface to top surface of a dielectric base. In the feeding radiation electrode, a slit that extends from a feeding end in an inward direction is formed, and, in the non-feeding radiation electrode, a slit that extends from a ground end in an inward direction is formed. In addition, on the non-feeding radiation electrode, a branch electrode is formed so as to extend toward the side of the feeding radiation electrode. With this configuration, gain is obtained in two frequency bands by using a multi-resonance of fundamental wave resonances and harmonic resonances generated by the feeding radiation electrode and the non-feeding radiation electrode, and a good return loss characteristic caused by coupling of harmonic resonances is provided. In other embodiments, the feeding and non-feeding radiation electrodes may be formed on a flat substrate, or directly on a circuit board.