A class configuration generation unit generates (n−1) number of class configurations each of which is comprised of i number of the already selected features plus a feature selected from the remaining (n−i) number of the features (both of n and i are integers). A class configuration selection unit selects an optimal class configuration from the (n−i) number of the class configurations using an arbitrary evaluation value. The features used in the class configuration selected by the selection unit are used as the already selected features in the generation unit. The operations by the generation unit and the selection unit are repeated with values of i sequentially varying from 0 to r−1, thereby generating a class configuration comprised of r number of the features.