PURPOSE: To provide a feedback system which secures both the target value following performance and the disturbance suppressing performance.

CONSTITUTION: A1st controller 12 which excels in the target following performance is provided together with a 2nd controller 14 which excels in the disturbance suppressing performance. The outputs of both controllers 12 and 14 are selected by a switch 16 and given to a controlled system 4. A deviation detector 18 operatus the deviation E between the controlled variable and the target value. A changing rate arithmetic circuit 8 operates changing rate ΔE based on the deviation E. A proper mode deciding circuit 10 outputs a target value following action mode signal if the codes of the deviation E and the rate ΔE are different from each other. If these codes are equal to each other, the circuit 10 outputs a disturbance suppressing action mode signal. The switch 16 receives the target value following action mode signal to select the controller 12 and then receives the disturbance suppressing action mode signal to select the controller 14 respectively.