A new topology analysis method was developed to optimize part shapes and the configuration of automotive components. Only solid elements are used in the conventional topology optimization method. The key point of the new method is to embed solid elements in a model made of shell elements. In this study, stiffness optimizations were carried out for a simple cylindrical model, automotive floor model and full vehicle model. Specifically, optimized automotive components were a center tunnel, a side-sill and a joint linking a side-member and a cross-member, which are made of steel sheets and have rectangular cross sections. The results show that the newly-developed topology optimization method is valuable in the optimization of automotive components which are made of steel sheets and have rectangular cross sections.