To provide the correlator for spread spectrum communication which extends neither the initial pull-in time and nor the circuit scale.

An in-phase component signal I and an orthogonal component signal Q from a reception part 1 are given to low-precision matching filters 2 and 3 respectively, and outputs of these filters 2 and 3 are given to square circuits 4 and 5 respectively and are squared and outputted. Outputs of square circuits 4 and 5 are added by an adder 6 to obtain the envelope output of the input signal, and a level discrimination part 7 obtains and outputs the phase difference between the time position of a maximum value in one symbol time and a local spreading code from the envelope output. A phase locked loop 8 sends a sample rate clock synchronously with the input spreading code, and a correlator 9 with a time window takes correlations between the in-phase component signal I or the like of the chip in a prescribed time window and the local spreading code.