1. An onboard information terminal comprising: a map information storing section for storing at least road data; 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 road data stored in the map information storing section, a new road data for adding a new road to a road network, which is represented by the road data 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 new road data generated by said road data generating section and the road data stored in said map information storing section; wherein the road data generation section makes a decision whether the new road data connects with the road data stored in the map information storing section or not, and if the road data generation section decide that the new road data connects with the road data stored in the map information storing section, the map information update section adds connection relationship with the new road to the road data stored in the map information storing section.