A map-updating-data creating apparatus performs, for each old map file, creating a map-updating file for rewriting the map file to a new map file, determining the serial number of each of the updated map files, creating a serial number management file in which marks are respectively written at positions corresponding to the serial numbers, and generating, as map-updating data, the map-updating file and the serial number management file. A navigation apparatus performs map-updating processing and determines, by referring to the serial number management file, whether a map file has already been updated. The navigation apparatus uses the map-updating file to execute navigation control if the map file has already been updated, and updates the map file and subsequently executes the navigation control if the map file has not been updated.