In proposing the jumping mechanism imitating the leg of vertebrate, unique mechanical function of bi-articular muscle was analyzed. The bi-articular muscle is an actuator which exists only in vertebrate. The ground reaction force and/or jumping motion were examined using the following three jumping mechanisms, 1) the mechanism which arranged two actuators on the knee and ankle joint independently (Mechanism-A), 2) the mechanism which arranged two actuators on the knee and ankle joint, and connected two joints by a wire (Mechanism-B), 3) the mechanism which arranged one actuator only on the knee joint, and connected two joints by a wire (Mechanism-C). It became clear that the Mechanism-C is excellent as the result of analyses in this study. A pantograph mechanism is constituted by the wire equivalent to the biarticular muscle which transmits the joint torque between two joints. And, ideal ground reaction force for jumping motion is generated. Furthermore, the jumping mechanism or robot which has the function of bi-articular muscle was made and the vertebrate like jumping motion was realized. In this study, it is said that the muscular arrangement of vertebrate is ideal arrangement. It is also an answer to the general question why is the crus very thinner than the femur of vertebrate which makes a jump elated.