PURPOSE: To shorten time up to reacquisition when out-of-synchronism occurs by speeding up synchronizing time by changing forcedly a spread code by a spread code setting circuit when an unlock detection circuit detects the out-of- synchronism of a synchronous part PLL.

CONSTITUTION: The synchronous part 2 to generate the spread code synchronized with a received spread spectrum signal is constituted of a PLL circuit. When electric field intensity is changed and the out-of-synchronism occurs while the PLL is in a locked state, a phase error signal appears in the output of a phase comparator PD4. The unlock detection circuit 10 detects the unlocked state of this PLL, and closes a switch 12 by an unlock state detection signal so as to connect a preset signal line from a PN code setting circuit 11 to a PN code generator 8. Thus, the circuit 11 executes presetting so as to change successively a state. Owing to this change, the oscillation frequency of a VCXO 6 is changed, and the PLL is driven into the locked state, and the circuit 10 opens the switch 12, and interrupts the preset signal line, and holds the locked state of the PLL.