Abstract: A GPS receiver apparatus retrieves a maximum correlation point between a PN code involved in a satellite signal and a generated PN code with use of n detecting means each concurrently processing the retrieval operation to acquire the PN code of the satellite signal. The apparatus acquires the PN code of the satellite signal, unless said maximum correlation is yielded, by effecting a correlation processing or taking the synchronization among phases of the PN code in which the generated PN code is shifted in its phase by n/2 bits to retrieve the maximum correlation point. The apparatus further tracks GPS radiowaves with the use of a plurality of said detecting means which has been used to acquire the PN code.