Road map data includes node data indicating a branch point, a junction point, or an intersection point and link data indicating a road between the preceding points. The node data and link data include distances, kinds of the roads, costs based on easiness of traveling. In a route search, a route is selected so that a total cost included in traveling on the route to a destination can be minimum. When command is generated as giving priority to an automatic travel road, costs included in the node and link data that correspond to the automatic travel road are lowered. A route including the automatic travel road is thereby selected in preference to other routes.