Update method of map data and map information system

An update method of map data executed by a map information system provided in a vehicle, wherein

• the map data includes multiple pieces of block data separated so as to correspond to blocks on a map and stored in a storage device of the map information system, and
• wherein the map information system
• decides priority orders of pieces of block data to be updated based on at least one of a position of an own vehicle, a route to a destination, and a passage history,
• communicates with a map server having a latest version of the map data and downloads update data of the pieces of block data to be updated from the map server in accordance with the priority order,
• updates the pieces of block data stored in the storage device based on the downloaded update data, and
• when, during download of a piece of block data, a corresponding block does not include the route to the destination and is positioned behind the own vehicle with respect to the direction of the own vehicle, the map information system cancels the download of the piece of block data that is being downloaded, the corresponding block being a block corresponding to the update data that is being downloaded.