A mechanism is provided for enabling prediction of a cost between an origin and a destination even in the case of insufficient past route information. Data D, which includes an origin, a destination, and information on cost between these points, is prepared as well as a subroutine for calculating cost ce along an arbitrary link e on the basis of the set along with a variable denoted by fe. In the first step, the minimum cost route is found from the current {fe} with respect to all pairs of the origin and the destination included in the data D, thereby forming transformed data D′. {fe} is recalculated by using the above subroutine from D′ by computer processing and then compared with {fe} calculated last time. If a change is equal to or greater than a threshold, control returns to finding the minimum cost route. Otherwise, {fe} is fixed.