We are developing a new walking support machine for old people and handicapped people, because they expect to move easily by themselves. The machine is equipped with two ER devices which compose a elctrorheological fluid clutch (ER clutch) and a motor, and able to work with smooth power assistance or safety breaking. In this paper, we refer a developing concept in the new walking support system, and explain a mechanism and design of the ER devices. In addition, we also report some experimental results, because we have examined on characteristics of the ER devices.