The purpose of this study is to develop an optimum design method for roof shapes that satisfy the conditions of both beauty and dynamics by using a GA (genetic algorithm). The plane form of the building is a rectangle, and the design target is a concrete roof that covers this plane. The roof shapes were evaluated from the viewpoints of stress values and beauty. The stress values were obtained by FEM (finite element method) analysis. Additionally, the relationship between the roof shapes and beauty was investigated using questionnaires based on computer graphics. These results were analyzed to formulate KANSEI evaluation rules that incorporated the beauty and the elements of form. By using these rules, the degree of beauty of the roof shapes created using the GA could be estimated. A synthetic evaluation value was estimated from the two evaluation values adopted in this study. The roof shape that exhibits the lowest synthetic evaluation value was created by the genetic operation.