A ground conductor constituting a bottom board and a loop antenna formed of a strip conductor formed separately from and around the ground conductor are provided on one face of a dielectric substrate, and a transmitter-receiver is connected to one end of the loop antenna serving as the power dispatching unit via a first matching circuit, and a second matching circuit is connected to the other end. A conductor formed of the strip conductor is provided on the dielectric substrate on the other face of the dielectric substrate so as to oppose the loop antenna with the intermediary of the dielectric substrate. A third matching circuit is connected to one end of the conductor and a fourth matching circuit is connected to the other end of the conductor. The loop antenna and the conductor are set to have a wavelength shorter than that of the frequency band to be used.