To conquer the problem of weakness for multi-path phasing while using quadrature frequency modulation by multiplying a spreading code synchronized to a spread high frequency signal, which is received at a reception part, to this spread high frequency signal and demodulating the quadrature frequency multiplex signal of the multiplied result.

A transmission part 3 converts transmission data, which are converted to quadrature signals, to high frequency signals through a CPU 2, makes these signals into direct spread signals by multiplying them through a multiplier and outputs them to a high frequency part 5. While receiving the reception signals of radio frequency from the high frequency part 5, a reception part 4 generates a synchronizing signal following up the received synchronizing signal based on a correlation detecting signal through a synchronous follow-up circuit, and the spreading code according to this synchronizing signal is generated by a spreading code generator. Then, the received signal of radio frequency and this spreading code are multiplied by the multiplier and a spread frequency is converted to the original quadrature frequency signal. Then, the quadrature frequency multiplex signal of the multiplied result is demodulated.