Abstract: 3-D structure design system and method thereof capable of preparing drawings and performing quantity calculation at the same time, and largely eliminating troubles caused when designing a concrete structure by handling the design of concrete-made structures with a cubic 3-D data from the very beginning. The system comprising: data input device for inputting structure data; 3-D structural data search device for searching data on a portion between members and data on a connection between members on the basis of the input data on the concrete-made structure, checking an interference portion between members, aligning members through the result of rivaling between members, automatically adjusting the overlapping of members, and searching the input data on members as data conforming to the concrete structure; body quantities search device for calculation; and result display device for displaying/outputting a search result.