A reference local oscillation signal transmission station 1 radiates a reference local oscillation signal to a service zone. A portion of the signal received by each radio slave station terminal 2 is branched and fed to an injection locked oscillator 6. As a result, a local oscillation signal which is synchronized with the reference local oscillation signal is obtained. In the slave station terminal 2, the thus-obtained local oscillation signal is fed to a transmission frequency converter (mixer) 7 and a reception frequency converter (mixer) 8. An IF band transmission modulated signal is fed to the mixer 7 for frequency conversion to a radio frequency band, and the thus-obtained radio-frequency modulated signal is transmitted. Meanwhile, a received radio-frequency modulated signal is fed to the mixer 8 for down conversion, and the thus-obtained signal is fed to an IF band demodulator 10 so as to restore an information signal. The present invention not only solves the problem of deterioration of signal quality stemming from phase noise and frequency offset generated in a millimeter wave band oscillator, but also improves the efficiency of frequency use.