A car navigation system 1 includes a HDD map 110 and a cached map 109. Map data for entire area is stored in the HDD, and map data used by a route search unit 115 and a guidance unit 116 are stored in the cached map 109. A cached map area specifying unit 108 specifies map data files that should be stored in the cached map 109 for each navigation application, and stores the names of the specified map data files, linked to the respective navigation applications, into a navigation application consistency management table 103. A consistency judgment unit 104 monitors an update status of a data file of which name stored in the navigation application consistency management table 103, and stores the update status (completed or not completed) into the navigation application consistency management table 103.