The purpose of this study is to develop a gait training system for elderly and disabled people. The developed gait training system comprises a long-leg brace with trunk support and is driven by pneumatic Mckibben actuators. The gait training system developed in our previous study was controlled by an open-loop circuit. In this study, we attempted to develop a feedback control system which referred difference between inner pressures of actuators set up in an antagonistic arrangement. This system, however, was unable to represent completely natural human walking because the feedback parameter did not include hip and knee joint angle information. We then used a control method wherein the difference between the inner pressures of the agonistic and antagonistic Mckibben actuators was used as the input data and a proportional directional control valve was used to simultaneously activate the actuators. This control method increased the stiffness of the hip and knee joints of the orthosis. Thus, we successfully developed an inner pressure difference control system to drive a gait training system.