When updating means 24 for performing a differential update on map data M using update data U performs an update on the map data M using update data U stored on a recording medium R, update data U having section identification information that matches the section identification information of the map data M and a later update version than the update version of the map data M are extracted from the plurality of update data U stored on the recording medium R, and a differential update is performed on the map data M using the extracted update data U.