Hydraulic actuation has the advantage of substantial power and wide range of speed with a small size and low weight. Because of this advantage, hydraulic actuation is used often for a robot dealing with heavy-weight material or walking fast. However, in a walking robot, the power of hydraulic actuator can act as the ground reaction forces between the feet and the ground surface, breaking the balance of the body. Therefore, compact design of a body including the feet and module design for absorption of the ground reaction forces is critical. This paper explains leg design for compact design of hydraulic actuated quadruped robot. Also, this paper describes about a shock absorber design included in the feet module by walking-in-place experiments.