PURPOSE: To facilitate editing such as adding, correcting, deleting, etc., a fuzzy rule.

CONSTITUTION: Concerning the fuzzy rule stored in a knowledge storage part 1, a conversion processing part 4 generates first display data concerning in a state of a matrix, which consists of the name of a membership function given to first and second input variables and the name of a membership function given to corresponding output variables and second display data concerning the other fuzzy rules which can not be expressed in first display data with an input from an input part 2 and stores them in a display data storage part 7. At the time of updating the fuzzy rule, the conversion processing part 4 reads pertient first and second display data to display them on a display part 3 with the input from the input part 2, and adds, corrects and deletes the fuzzy rule with respect to first and second display data with the input from the input part 2 so as to update display data and the contents of the pertient fuzzy rule in the knowledge storage part 1.