PURPOSE: To enable a spread spectrum-modulated signal to be demodulated by attaching a pulse on or eliminating it from a PN clock signal inputted to a PN code output circuit.

CONSTITUTION: When no pulse signal P7 exists, a pulse signal P6 on which one pulse is attached is outputted as the PN clock signal, however, when the pulse signal P7 exists, a signal from which the pulse is eliminated is outputted at the timing of a pulse signal P3 as the PN clock signal. The PN code output circuit 9 outputs a PN code P9 based on the PN code signal P8. In such a way, when the code of transmission/reception is recognized, it is possible to take synchronism of the PN code by leading or lugging the PN clock signal by operating an up-count signal output means 10a or a down-count signal output means 10b.