This paper introduces an elevator design support system which employs case-based reasoning techniques. The system analyzes elevator specifications, generates indices, retrieves similar cases from a case base, and shows the retrieved cases to elevator designers. The biggest issue in applying case-based reasoning techniques is retrieval of appropriate cases. For the appropriate retrieval, indices of the cases and the definitions of similarities among the cases are correctly chosen. In elevator specifications with many items, it is extremely difficult to make the whole structure of the specifications clear for choosing indices and defining the similarities among the specifications. In order to overcome the difficulty, a new indexing method which uses heuristics of the designers is developed. Also, the system provides the designers with flexible retrieval ways, so that the designers can refer the cases from various points of view.