An optical-wireless hybrid transmission system in which a central office has an optical transmitter and an optical receiver, said optical transmitter transmits an optical carrier signal to a base station via an optical transmission line, said base station receives an RF signal at frequency f RF (f RF) that is modulated according to transmit-data, optically modulates said optical carrier signal according to the received RF signal, and transmits a resulting modulated optical signal to said central office via an optical transmission line, and said optical receiver receives and demodulates the modulated optical signal and reproduces said transmit-data, the system characterized in that said optical transmitter comprises: a first single-mode optical source which outputs a first single-mode optical signal at a first center frequency f C1 (f C1); a second single-mode optical source which outputs a second single-mode optical signal at a second center frequency f C2 (f C2); a third single-mode optical source which outputs a third single-mode optical signal at a third center frequency f C3 (f C3); and a polarization-coupling part which orthogonal-polarization-couples said second single-mode optical signal with said third single-mode optical signal while adjusting polarization directions and optical powers of two waves so as to make the polarization directions orthogonal and the optical powers identical, and outputs a resulting polarization-coupled optical signal, in which the center frequencies f C1, f C2, and f C3 of said first, second, and third single-mode optical signals are controlled so as to satisfy | f C 1 − f C 2 | = f RF ± f IF 1 | f C 1 − f C 3 | = f RF ± f IF 2 where f RF is a frequency of said RF signal and f IF1 and f IF2 are prescribed intermediate frequencies; and said first single-mode optical signal is transmitted to said base station as said optical carrier signal and said polarization-coupled optical signal is output to said optical receiver; and that said optical receiver comprises: an optical coupler which couples the modulated optical signal transmitted from said base station with said polarization-coupled optical signal output from said optical transmitter; a photodetector which photodetects a coupled optical signal output from said optical coupler, and thereby outputs an electrical signal having the intermediate frequencies f IF1 and f IF2; an electrical demodulator which demodulates the electrical signal having the intermediate frequencies f IF1 and f IF2 and output from said photodetector; and a low-pass filter which filters an output signal of said electrical demodulator and thereby outputs said transmit-data. a first single-mode optical source which outputs a first single-mode optical signal at a first center frequency f C1 (f C1); a second single-mode optical source which outputs a second single-mode optical signal at a second center frequency f C2 (f C2); a third single-mode optical source which outputs a third single-mode optical signal at a third center frequency f C3 (f C3); and a polarization-coupling part which orthogonal-polarization-couples said second single-mode optical signal with said third single-mode optical signal while adjusting polarization directions and optical powers of two waves so as to make the polarization directions orthogonal and the optical powers identical, and outputs a resulting polarization-coupled optical signal, in which the center frequencies f C1, f C2, and f C3 of said first, second, and third single-mode optical signals are controlled so as to satisfy | f C 1 − f C 2 | = f RF ± f IF 1 | f C 1 − f C 3 | = f RF ± f IF 2 where f RF is a frequency of said RF signal and f IF1 and f IF2 are prescribed intermediate frequencies; and said first single-mode optical signal is transmitted to said base station as said optical carrier signal and said polarization-coupled optical signal is output to said optical receiver; and that said optical receiver comprises: an optical coupler which couples the modulated optical signal transmitted from said base station with said polarization-coupled optical signal output from said optical transmitter; a photodetector which photodetects a coupled optical signal output from said optical coupler, and thereby outputs an electrical signal having the intermediate frequencies f IF1 and f IF2; an electrical demodulator which demodulates the electrical signal having the intermediate frequencies f IF1 and f IF2 and output from said photodetector; and a low-pass filter which filters an output signal of said electrical demodulator and thereby outputs said transmit-data. an optical coupler which couples the modulated optical signal transmitted from said base station with said polarization-coupled optical signal output from said optical transmitter; a photodetector which photodetects a coupled optical signal output from said optical coupler, and thereby outputs an electrical signal having the intermediate frequencies f IF1 and f IF2; an electrical demodulator which demodulates the electrical signal having the intermediate frequencies f IF1 and f IF2 and output from said photodetector; and a low-pass filter which filters an output signal of said electrical demodulator and thereby outputs said transmit-data.