With respect to a non-road region route, which is in a region other than roads registered in map data, a navigation apparatus in a vehicle specifies three check items: travel times the vehicle traveled; a shortened distance reduced by traveling the non-road region route compared with a route registered in the map data; and presence or absence of a predetermined facility in the vicinity of the non-road region route. The navigation apparatus determines an accuracy degree as to whether the non-road region route is existent based on the specified check items, thereby determining whether the non-road region route is existent. A route guidance process is executed based on the non-road region route, which is determined to be existent.