To estimate a more accurate transit time to a route without including traffic information.

A reference route searching the route without using the traffic information includes a traffic information section, and a detour route using the traffic information does not include the traffic information section. When the route is searched from the same start point to a destination point, knowledge of t2>t1 and T1T2t1 is obtained in the case that a forecast transit time of the reference route is t1 (using traffic information), a real transit time is T1, a forecast transit time of the detour route is t2 and a real time transit is T2. A forecast transit time with higher precision can be made by predicting the forecast transit time t1 of the reference route R1 as the forecast transit time of the detour route R2.