In the authors' 1st report, a smart and simplified self-sensing actuator technique using piezoelectric films with different thickness is proposed. In this paper, application of the proposed method to the vibration control of curved structures is investigated. A flexible circular ring is treated as an example of curved structures and piezoelectric films with different thickness are bonded on one surface of the ring. The two films are treated as two capacitors in the active RC bridge circuit, and these are totally used as a self-sensing actuator. At first, fundamental equations of the circular ring with proposed self-sensing actuator are derived and vibration control effects are estimated by numerical analysis. Then, vibration control experiment is performed using an aluminum circular ring, and it is shown that the lowest vibration mode is efficiently controlled.