This paper presents the vibration control system of a simply supported beam, which is subjected to external forces, and a simply supported rotating shaft which has unbalances. When a sustained disturbance is subiected to a flexible structure, the optimal control can't Provide significant reduction in vibration. For further reduction of the vibration, the disturbance cancellation control method is applied to a design of control system together with the optimal control. The disturbance cancellation control is introduced by estimating the position and magnitude of disturbance by sensing the acceleration of them. By carrying out numerical calculations, it is demonstrated that the present design approach is useful for reduction of the vibration in broad frequency band.