Abstract: A truth value generator circuit array (11) includes truth value generator circuits (TG1-TG3) the number of which is the same as the number of kinds of input variables. Each truth value generator circuit generates truth values, which correspond to an applied input variable, with regard to a plurality of predetermined functions used by the antecedent of implications. The truth-valued-flow inference unit array includes truth-value-flow inference units (TVFI1-TVFI7) the number of which is the same as the number of predetermined functions used by the consequent of implications. Each truth-valued-flow inference unit corresponds to each function used by the consequent. All truth values outputted by the truth value generator circuit array enter each of the truth-valued-flow inference units. Each truth-valued-flow inference unit selects input truth values in accordance with predetermined rules and subjects these truth values to a prescribed operation.