PURPOSE: To produce a solid model based on plural incomplete drawings.

CONSTITUTION: The segments and curves of three drawings are calculated from the two-dimensional data on these drawings, and a wire frame model is produced based on those calculated segments and curves. The edge line of the wire frame model is compared with the segments or curves for correction of the frame model. Then the corrected wire frame model is converted into a sell division model. The conditions that correct at least one of three drawings are set by a Boolean equation, and a solid model is synthesized based on the combination of cells, i.e., the solution of the equation. When no solution is obtained from the equation, the candidate models are synthesized based on the optional combinations of cells. These candidate models are displayed in the order of higher resemblance. Meanwhile a candidate model is selected by an operator as a solid model when plural combinations of cells are obtained as the solutions. Then, three drawings are newly produced for the acquired solid model, and the original three drawings are completed based on these new drawings.