Power assist gloves support the holding force and the gripping motion of hands. They should be light and not lose the feeling of touch to be used in daily life. In this study, we develop a power assist glove that combined a skeletal structure and a pneumatically driven actuator. The actuator is made by thermally welding a plastic film. This actuator expands and oscillates when pressure is applied. This allows the mechanism to be attached to the back of the hand, reducing the area covered by the palm. In this study, the structure of the mechanism and the design of the actuator are investigated, and the performance of the mechanism is evaluated by measuring the output using a 6-axis force sensor and analyzing the grasping posture of a grasped object.