A switching unit which switches the sub antenna, which is for performing diversity reception in cooperation with the main antenna for transmission and reception, from functioning as an antenna to functioning as a parasitic element, or from functioning as a parasitic element to functioning as an antenna, is provided; the main antenna and the sub antenna are provided to be spaced a predetermined distance apart so that multiple resonance can be generated by electromagnetic coupling, and the sub antenna is made to function as a parasitic element to generate multiple resonance, widening the frequency band width within which the main antenna can transmit and receive a radio wave.