PURPOSE: To obtain an antenna circuit of the radio communication device which is not increased in current consumption and attenuates a large signal causing distortion.

CONSTITUTION: A flat plate 22 and an earth plate 21 are arranged having their surfaces faced to each other and the both are short-circuited by a short-circuit plate 23 which has width W. Further, switches SW1 and SW2 which short-circuit the flat plate 22 and earth plate 21 are provided at positions parallel to the short-circuit plate 23. If a large signal is received and distortion is caused, the flat plate 22 and earth plate 21 are short-circuited by operating the switches SW1 and SW2 to vary the resonance frequency of the antenna 11 consisting of the flat plate 22, earth plate 21, and short-circuit plate 23. Consequently the, deviation of tuning by variation portion in resonance frequency is caused and then the received signal is attenuated correspondingly.