An evaluation point E of a present position candidate corresponding to each satellite set is calculated based on an a priori residual (APR) (APR value), a PDOP value, and the number of satellites of the target satellite set according to E=k1·f1(APR)+k2·f2(PDOP)+k3·f3(number of satellites). Evaluation coefficients k1 to k3 for respectively weighting evaluation functions f1 to f3 are determined based on an APR average value.