The present invention provides technology that updates a map such that appropriate guidance can be provided near an intersection. A map data update system updates map data on a link-by-link basis and includes a link acquisition portion that acquires an existing link which is a link indicated by existing map data and a new link which is a link indicated by new map data, and a link update portion that updates the existing link with the new link based on a shape of a portion of the existing link connected to an intersection and a shape of a portion of the new link corresponding to the existing link, the portion being connected to the intersection.