A map difference data distribution system includes a map difference data distribution device including a map difference data storage unit storing map difference data items and a distribution unit distributing map difference data items, and a map data maintaining device including update unit updating map data based on map difference data items. The map difference data storage unit traces the updated data items and data items having dependent relationships with the updated data items back to the different version updates, and stores the data items as map difference data items. The map difference data distribution device includes a non-updated data extraction unit extracting non-updated data items from the map data maintaining device, a grouping unit grouping the data items in dependent relationships, and a distribution data generation unit generating distribution data by arranging grouped records of non-updated data items from higher priority of map element under specified communication traffic volume.