To provide an on board navigation system which allows retrieval of a route in conformity with the vehicle on which it is mounted.

A user inputs the kind of a vehicle (compact, normal, large. special) from a control part 2 when installing a navigation system in the vehicle. The kind of the vehicle input is stored in a vehicle kind storage memory 16. During retrieval of a route, a control part 15 sets retrieving conditions according to the kind of the vehicle to retrieve the route in such a way as to avoid roads of small widths which the vehicle cannot pass and roads with height or weight restrictions.