Even though large scale of structures are usually carried by dock side crane, few studies have been done on the technology in the erection stage for shipbuilding. The reason is that those technologies have been thus far supported by the highly skilled people. Now situations is radically changing with respect to human resources. We are facing the problem that we will not be relied on the skillful people. In order to overcome this problem, computer aided technolgy is thought as one of the most powerful methods. In this paper, a computer simulation system for the erection stage is considerd by using SODAS (System Of Design and Assembling for Shipbuilding). Some simulation results are shown in this paper.