This paper proposes an approach to extracting features of origami works which are recognized from facing page images of instructions described as origami drill books. The origami work is presented as a set of faces (polygons). First, in order to associate geometric shapes of objects with knowledge, an origami data model based on design knowledge is proposed. Therefore, the set of faces is classified into clusters which indicate a certain meaning in origami design. The cluster is called "origami molecule". Next, the relationships among the molecules are defined. The relationships are not only connected relationships but also symmetrical relationships and equivalence relationships. By using these relationships, it is possible to comprehend twin parts of origami work, for example, two forefeet of the fourlimbed creature. Finally, a method for extraction of the design knowledge from crease patterns is proposed.