A system and method for inputting two-dimensional drawing data and classifying that drawing data into plan view data and sectional view data. Closed regions and inclusion relations among the respective closed regions are detected from the classified plan view data. Attributes of the detected closed regions are detected, and the detected closed regions are grouped into groups, each including closed regions of the same attributes based on the detected attributes of the closed regions. The sectional view data is divided on the basis of data on the detected closed regions. Some of the closed regions are three-dimensionalized based on the divided sectional view data. Closed regions not belonging to the three-dimensionalized portion of the closed regions but belonging to the same group as a three-dimensionalized closed region are three-dimensionalized by the same method as was used for the three-dimensionalized closed region. A solid model is generated by combining the three-dimensionalized closed regions through Boolean operations performed on the basis of the inclusion relation among the respective closed regions.