According to a navigation server (1) of the present invention, in a mileage matrix containing elements which denote a mileage and are defined by respective mileage factors, a first element of the elements in the mileage matrix which is defined by recognized mileage factors is determined on the basis of the mileage of the recognized mileage of a first vehicle. A second element of the elements in the mileage matrix which is defined by unrecognized mileage factors is determined on the basis of the first element. According thereto, even when the mileage factors of a second vehicle are used to define the second element but not the first element, the previous mileage of the second vehicle can be evaluated with high accuracy in consideration of a relationship between the mileage and the mileage factors of the first vehicle estimated according to the known relationship therebetween.