1. An onboard information terminal comprising: a map information storing section for storing map information; a distribution information acquiring section for obtaining, from outside, distribution road information containing coordinate point string data consisting of a series of coordinate points indicating geographical positions; a road data generating section for generating, in the same format at least in part as the map information, road data for adding a new road to a road network, which is represented by the map information stored in said map information storing section, from the coordinate point string data contained in the distribution road information obtained by said distribution information acquiring section; and a map information update section for generating new map information from the road data generated by said road data generating section and the map information stored in said map information storing section.