A cell phone antenna switching circuit includes a plurality of built-in antennas which perform radio transmission/reception. This circuit includes reception level measuring sections and an antenna switching section. The reception level measuring sections measure the reception levels of the corresponding built-in antennas. The antenna switching section always automatically selects an antenna whose reception level is high during a standby period, and selects an antenna with good antenna characteristics depending on a function during speech communication. A cell phone antenna switching method is also disclosed.