In this paper, a fault tolerant controller design method is proposed. It assures the integrity against actuator and sensor faults. While some controller design methods to assure integrity have been proposed, they assumed that the plant was stable. The proposed method in this paper assures the integrity even for unstable plants. To avoid making the controller too conservative, the possibility of the failure is limited to one actuator or one sensor. In addition to the integrity, the quadratic control performance is given to the design problem. Therefore, the fastest controller, which assures integrity, can be designed.