PURPOSE: To easily and inexpensively demodulate data by utilizing a spreading code included in a transmitted spreading signal without using data of consecutive spreading codes at the time of demodulation.

CONSTITUTION: A graphic (a) shows a spectrum spreading signal for differential- BPSK-demodulating at prescribed transmitting periods and (b) shows a signal for receiving the spectrum spreading signal and delay-detecting it. In (a), 0 in original data D1 (0, 1) is converted to different data (1, 0) of the front and rear and 1 is converted to the same data (0, 0) of front and rear to be D2 (1, 0, 0) as a whole, and they are furthermore converted to a spectrum spreading signal S1 for transmitting by spreading by data of 6 bits. In (b), inputted spectrum spreading signal S1 is multiplied by a delay signal SDL1 for delaying by the period time T of the spreading code by a delay line 1 by means of a multiplier 2 to be a multiplying signal SDT1. Then, LPF3 cuts carrier frequency components into a detection signal and a data discrimination part 4 switches it to obtain a digital signal SD1.