In a map information processing apparatus including a processor 5 for updating map information containing map data stored in a map information storage device 3, road network data contained in the map data stored in the map information storage device has a data structure in which the road network data is composed of link strings each of which represents a series of roads in a road network as a series of links connecting nodes, the road network being represented by the nodes and the links; each of the link strings is represented by a link string record in which link records defining the links are arranged in order of the series of the links; each link constituting the link strings is provided with an invariable link identifier proper to each link; and node indication information for designating each node included in the link strings is represented by the link identifier of the link having the node as its one end.