To facilitate fixing of a navigation system by calculating the moving distance of a vehicle based on a moving distance coefficient and the frequency of AC component thereby detecting the position.

Based on a moving distance during a predetermined time determined from a positional transition detected by a position detecting means 16 and a frequency selected by a frequency selecting means 11, a moving distance coefficient calculating means 14 calculates a moving distance coefficient, i.e., the moving distance of a vehicle per one period of the frequency for each speed change stage. According to the moving distance coefficient, a correcting means 17 corrects the content stored in a moving distance coefficient memory means 18 and the content estimated by a speed change stage estimating means 12. Depending on a speed change stage estimated by the speed change stage estimating means 12, a moving distance calculating means 13 calculates the moving distance of the vehicle based on a moving distance coefficient obtained from the moving distance coefficient memory means 18 and a frequency selected by the frequency selecting means 11. The calculated moving distance is delivered to the position detecting means 16 where the current position is detected based on the moving distance and an orientation detected by an orientation detecting means 15.