This paper proposes a walking control design for the utilization of passive elastic trunk and shows the result. It is inferred that legged animals decrease negative work during walk by utilizing elastic elements: muscle and tendon. There are researches on legged robots by utilizing elastic elements as the elastic utilization of legged animals . However, there are no researches on the walking control design of the legged robot for elastic utilization. Therefore, we aim to achieve to decrease energy loss of the walk of a quadruped robot with a passive trunk.