A combined sectional view is produced by obtaining a section plane based on one of a plurality of section lines, which is currently set as a target, and on a cut face along the target section line, obtaining an adjacent section plane passing a crossed point between a connected section line, which is connected to the target section line, and the target section line and being perpendicular to a plane including the plurality of section lines and to the section plane, specifying one or more elements and/or parts of elements of a three-dimensional model, which are necessary to draw a sectional view of the model, with respect to the section plane and the adjacent section plane, projecting the specified elements and/or the parts of the elements to obtain a sectional view corresponding to the target section line, and combining a plurality of sectional views obtained by executing the above-described processes for each of the section lines.