PURPOSE: To realize a fuzzy operation circuit which has a high operation speed and a high integration degree and is less dependent upon used elements and has a high flexibility as the whole of the constitution by combining AND gates and OR gates.

CONSTITUTION: For the purpose of leading to conclusion A'→B' from rule A→B based on the MAMDANI inference method, a height (a) of a product set of fuzzy sets A and A' is obtained, and a conclusion set B has the top cut by the height (a) to obtain a conclusion B'. Therefore, logic gates are used where it is premised that pulses expressing the values of membership functions with corresponding durations are used as the input. A minimum value selecting circuit consists of an AND gate Ga and a maximum value selecting circuit consists of an OR gate Go, and maximum values in minimum values out of values of respective elements of sets A and A' are obtained and have the top cut by an AND gate Gm to obtain the conclusion B'. When each of sets A, B, and A' has n elements and there are m kinds of similar rules, the conclusion is obtained by the MAMDANI inference method.