A spreading code setting circuit generates N vectors, as spreading codes, which are +1 or −1 polarity and are unique to users. A multiplier multiplies the nth data and the nth spreading code corresponding thereto for the spread modulation. An FDM combining circuit modulates N pieces of data according to the FDM method. A FDM separating circuit demodulates received signals according to the FDM method. An inverse spreading code setting circuit generates N vectors, as inverse spreading codes, which are +1 or −1 polarity and are unique to users at the transmission side. A multiplier multiplies the nth data and the nth inverse spreading code corresponding thereto for inverse spread modulation.