In this paper, we design a new pneumatic actuator using metal bellows. Because this actuator has no sliding parts, there is no influence of friction forces. Therefore, it is expected that the actuator has good performance in positioning and generating exact desired forces. Furthermore, because external forces can be precisely measured through pressure sensors, the bellows actuator works as a force sensor. In order to use the bellows actuator as a force sensor (bellows sensor), we investigate the static and dynamic characteristics of the bellows actuator. Based on these experimental results, the capability of the bellows sensor becomes clear. We use the bellows actuator as a sensing actuator which works as a sensor and an actuator simultaneously. In addition, the effectiveness of the actuator is demonstrated through several experimental results. We design one joint of a robot which is antagonistically activated by the two bellows actuators. Based on some experimental results, we disclose the static and dynamic characteristics of the proposed robot and confirm that it can move flexibly following external forces by utilizing the force sensing ability.