To calculate a new estimated position on a road by use of an absolute position obtained from a present position on a road and a GPS (global positioning system) system as reference.

Based on a plurality of present positions on a road obtained by estimated position calculating means 18, a plurality of movement positions are calculated from a distance acquired from distance acquiring means 12 and a direction acquired from course acquiring means 13 by movement position calculating means 16. Next, a plurality of routes between a plurality of points in the vicinity of a road adjacent to an absolute position acquired by position acquiring means 14 being a GPS receiver and a plurality of movement positions are calculated by route calculating means 17. Lastly, a plurality of estimated positions are calculated on the route by estimated position calculating means 18, and these plurality of estimated positions are evaluated, and the most proper position by displaying present position selecting means 19 is displayed as a present position on a display 5.