To provide a radio circuit that adopts a modulation loop system suitable for miniaturization.

A B-frequency band VCO 7 is used for a VCO of a synthesizer used for a phase comparison reference signal in a modulation loop while transmitting an output of an A-frequency band VCO 6, that is, transmitting an A- frequency band signal, and the A-frequency band VCO 6 is used for the VCO of the synthesizer used for the phase comparison reference signal in the modulation loop while transmitting an output of the B-frequency band VCO 7, that is, during the transmission of a B-frequency band signal. The A-frequency band VCO 6 or the B-frequency band VCO 7 is used for a VCO for a local oscillation synthesizer during reception. Thus, the number of required VCOs is less than that of the conventional systems, and the circuit size can be made small.