A GPS receiver including a receiving portion for receiving a GPS signal, a PN code signal generator, a correlation detector including a reproduced carrier signal generator, and a phase difference detector is disclosed. A frequency and a phase of the reproduced carrier signal are controlled according to a correlation result to track the carrier signal in the GPS signal, the PN code signal generator generates the PN code with a phase thereof controlled by phase control data from the correlation result, and amplitudes of the GPS signal is repeatedly sampled at timings with a deviation from an edge of PN code signal from the PN code signal generator varied. A zero-cross point on the variation of the sampled amplitudes provides a phase difference. The total phase difference is derived by summing the phase control data and the phase difference. To more accurately detect the phase difference, an interpolation may be effected. The sampling timings may be collectively generated as a train of sampling signal. The variation may be stored to estimate the receiving condition, so that the phase controlling may be effected adaptively.