This paper describes the mechanism of a one-legged jumping robot that can mimic the muscular and skeletal system of a human leg. The jumping robot has a waist, a thigh, a shin, and a foot. It weighs 6.5 [kg], and is 594 [mm] tall. It has a total of 9 actuators: 6 mono-articular types and 3 bi-articular types. A pneumatic artificial muscle actuator that can expand radially and contract axially is used. The actuators for mono-articular and bi-articular muscles are installed in the rear and the front of the thigh and the shin for the muscles to antagonize each other. The effectiveness of the mechanism and the control of the robot are verified through motion experiments.