1. A sentence classification device characterized by comprising: a term list having a plurality of terms each comprising not less than one word; DT matrix generation means for generating a DT matrix two-dimensionally expressing a relationship between each document contained in a document set and said each term; DT matrix transformation means for generating a transformed DT matrix having clusters having blocks of associated documents by transforming the DT matrix obtained by said DT matrix generation means on the basis of a DM decomposition method used in a graph theory; and classification generation means for generating classifications associated with the document set on the basis of a relationship between each cluster on the transformed DT matrix obtained by said DT matrix transformation means and said each document classified according to the clusters.