In the preparation of a characteristic word list as one method of text mining, means for selecting an unnecessary word group that requires to be removed in advance is provided. Document IDs and a user ID are received from a client, and a characteristic word list is prepared from the document IDs and document information obtained in advance. Next, selected book IDs are obtained referring to the user ID and a user attribute table. On the basis of the obtained book IDs, unnecessary words are removed from the characteristic word list prepared by characteristic word list preparation program, and the characteristic word list from which the unnecessary words are removed is returned to the client as mining results.