Geographical, guide or search information and route information are stored in storage sections. An arithmetic section provides a route researching function with preference for the traveling direction of a vehicle. A route-calculating section is provided for re-calculating the route, and a route guide control system is also provided, inclusive of a route deviation-detecting section. The re-calculating section calculates either the shortest route from the point of deviation to the previous route or a new route to the destination. In case of the search of the shortest route to the previous route, the shortest route from the present location to the previous route is searched giving preference to the traveling direction, e.g. avoidance of a U-turn, on the basis of the search information relating to the immediate vicinity of the present location, so that the route to rejoin the previous route can be quickly calculated. In case of search of a new route, the whole route from the present location to the destination is searched, again giving weight to the present traveling direction, on the basis of the search information relating to the area between the present location and the destination, to guide the driver along a new route completely different from the previous one.