Abstract—Development of soft actuators for the power assisting devices and rehabilitation devices has been required based on aging society in Japan. However, a flexible actuator that can generate both larger force and longer displacement has not been developed. It is also difficult to realize a flexible displacement sensor with long stroke while deforming its form according to the actuator’s shape. In the previous study, the flexible actuator with larger force and longer stroke that can adjust its stroke by giving a stepping motion using pneumatic balloons and brakes was proposed and tested. However, the speed of the actuator is too slow to apply to rehabilitation motion. In this paper, the improved stepping actuator using pneumatic cylinders with two types of strokes instead of pneumatic balloons is described. The position control of the improved actuator is carried out. A flexible robot arm that can expand and contract using three improved stepping actuator is also proposed and tested. As a result, it can be confirmed that the attitude of the robot arm can be easily controlled by giving stepping motion of each actuator.