1. An apparatus for automatically generating a solid model from a plurality of plan views, comprising: extraction means for extracting information related to surfaces from the plan views; first generation means for generating candidate surfaces based on the information extracted by said extraction means; second generation means for generating candidate surfaces and candidate edge lines by obtaining intersecting lines among the candidate surfaces generated by said first generation means after the candidate surfaces are generated by said first generation means; third generation means for generating candidate solids by determining combinations of the candidate surfaces generated by said second generation means after the candidate surfaces are generated by said second generation means; and selection means for collating the candidate solids generated by said third generation means with the plan views and selecting a matching candidate solid as a solid model after the candidate solids are generated by said third generation means.