A method for selecting a route from a departure point to an arrival point includes acquiring information concerning a departure point and an arrival point and information concerning a route from the departure point to the arrival point; generating a plurality of basic routes; calculating a parameter of an evaluation function that yields the selected route as an optimum route; generating a new route using the calculated parameter, determining whether or not the generated new route is identical to the selected route; on a condition that the generated new route is not identical to the selected route, adding the generated new route to the basic routes, recalculating the parameter, generating a new route, and comparing the new route with the selected route; and if the new route is identical to the selected route, storing the parameter when the new data becomes identical to the selected route.