PURPOSE: To realize a selecting circuit of a small scale and high accuracy because selection of inhibition MF operation/passing MF operation in a fuzzy neuron can be executed by a simple switch circuit, and also, an analog inverter is not required for an inversion processing.

CONSTITUTION: In the fuzzy neuron constituted of an analog circuit provided with a circuit which can select one of a passing MF membership function operation or an inhibition MF operation by a selecting signal, this fuzzy neuron is provided with a switch 12 for selecting one of a grade of MF, or an E/I signal to which whether it is a passing MF function or an inhibition MF function is declared by a code of one bit by a binarized image signal, and a switch 15 for selecting one of the minimum value operation result or the maximum value operation result of an output of the switch 12 by a bit value of the E/I signal.