A fuzzy control unit includes a fuzzy inference unit forming a manipulated variable for controlling a plant such that a control response from the plant is made equal to a previously set target value, based on fuzzy control knowledge. An automatic tuning unit corrects the fuzzy control rules in accordance with the control response from the plant. The automatic tuning unit includes a response waveform memory storing a control response value from the plant, a rule grade memory for storing grade values of the fuzzy control rules for the control response from the plant, an ideal waveform memory for storing ideal control response values to be attained by the plant under control by the fuzzy control unit, and a control evaluating circuit evaluating the control operation of the fuzzy control unit based on the ideal response value and the control response value. The automatic tuning unit also includes a circuit for correcting a membership function of a consequent portion of the fuzzy control rules in accordance with the amount of correction and the rule grade.
