According to a display processing unit, dividing axes are arranged and the division number and a connection between classification results are simultaneously displayed by a polygonal line onto a parallel coordinate graph obtained as a polygonal line by plotting a classification result of every plural analysis items by a clustering processing unit onto an axis of each analysis item. An annual ring diagram showing a division number which is more proper as an annual ring is thicker is displayed. The display processing unit displays a tree diagram obtained as a processing result of a classification processing unit by a folding, sorting, or the like so as to be easily understood. An output processing unit converts an unknown rule discovered by the classification into a format which can be used in an external application and outputs it.