In recent years, compliant mechanisms have been paid to attention as new mechanisms to replace traditional rigid link mechanisms.Compliant mechanisms achieve a specified motion by deforming the structure elastically instead of relying on joint movements.Compared to traditional mechanisms, compliant mechanisms have several merits due to their monolithic structure without joints.Thus, the use of compliant mechanisms in mechanical products, medical instruments and MEMS can be expected to increase.In this research, we focus on a vehicle suspension as a promising application target of a compliant mechanism and propose an optimal design method for a suspension using on compliant mechanism or a compliant suspension.In design of a vehicle suspension system, there are various design requirements including both statistic and dynamic characteristics.In this research, suspension stroke, lateral rigidity, camber angle, roll center height and natural frequency of a whole suspension system are considered as key design requirements.To design a compliant suspension to meet these requirements, we extend our two-stage design method that consists of topology and shape optimization.In the 1st stage or topology optimization stage, a new objective function is formulated to optimize suspension stroke, lateral rigidity and natural frequency, which generates an initial concept of a compliant mechanism having high flexibility in a vertical direction, high rigidity in a lateral direction and appropriate dynamic characteristic.In the 2nd stage or shape optimization stage, suspension stroke and camber angle are used as objective functions, whereas stress constraint, roll center height, lateral rigidity and natural frequency of a whole suspension system are used as constraint conditions, which yields optimal shape of a compliant suspension.Since a traditional vehicle suspension system is a typical rigid-link mechanism, a compliant vehicle suspension has a considerable room to reduce weight and cost and to increase design flexibility.Raising of environmental awareness and oil price in these days or years ask to achieve further improvement of fuel efficiency of vehicles.A compliant vehicle suspension will be a great help to its requirement.