As CAE (Computer Aided Engineering) applications become increasingly precise, the knowledge and technical skill required to operate such applications has become more highly specialized. However, such tools have not been utilized in the initial design process of mechanical products, where designers cannot construct detailed analytical models. This paper proposes a cross-sectional shape design optimization system that supports the initial design process for bar structures. The cross-sectional design problem is formulated as an eight-objective optimization problem that can be solved using genetic algorithms. A method for generating cross-sectional shapes satisfying designer-required characteristics is also proposed. These methods, which reduce the number of trial and error processes and product design failures, are expected to enable shortened product development lead-times.