A vehicle navigation system includes: a route guidance element for searching an optimum route from a current position of a vehicle to a destination according to a normal map data and for guiding the optimum route by displaying the optimum route on a map screen image of a display; a deviation route retrieving element for retrieving a deviation route, which has a possibility that a user may deviate from the optimum route and enter into the deviation route although the vehicle is incapable of driving along the deviation route; and an attention notification element for outputting attention notification information in order to prevent the user from entering into the deviation route when the route guidance element guides the optimum route.