In recent years, novel surgical planning methods based on computer visualization using preoperative CT images have been developed. Although they enable surgeons to perform accurate operations with surgical navigation systems and robots, they cause low reproducibility of placement and much manual manipulation on 3D planning systems, because of increase of dimensions of parameter space to be searched (e.g. depth direction) compared with the conventional 2D planning. Therefore, we objectified the expertise on planning of experienced surgeons and developed the automated planning system for a femoral stem in total hip replacement. In this paper, an automated preoperative planning procedure for acetabular cup, which is a hemisphere implant placed in the pelvic bone, is described. The algorithm is based on multiple criteria for evaluating stability of the cup and suitability with the host bone, which include host bone thickness, cup teardrop line displacement, cup center-edge angle, and cup bone coverage ratio. We define the optimal state of cup placement as a solution, which maximizes cup bone coverage ratio and fulfills the restrictions of other criteria. The solution is searched within the limited 3D zone determined by anatomical feature data. We applied the proposed algorithm to 18 cases and compared computer planning with expert surgeon's planning and apprentice surgeon's. The average differences between computer planning and expert surgeon's planning were 3.94 mm in position and 1.44 mm in size. 16 out of 18 computer planning were judged as acceptable or almost passable by both of the surgeons and only two cases were judged as a failure. We also tested variation of cup-teardrop line displacement threshold and confirmed that it is possible to customize the automated planning according to the surgeon's tendency. These results showed a potential usefulness of automated planning.