PURPOSE: To save an invalid processing at the time of a fuzzy inference, and to attain the high speed of the processing.

CONSTITUTION: The prescribed bit of a one bite rule code is used as the identification bit of the presence or absence of a condition. When the absence of the condition in a specific input item is judged (S104), the adaptability of the label of the condition is necessarily 1, and a processing is transferred to the next condition processing (S107) without operating an adaptability calculation (S105) or an MIN arithmetic operation (S106). And also, when the adaptability of the label of an input value is 0, the adaptability of the rule is necessarily 0 by the MIN arithmetic operation, and the processing is transferred to the next rule (S108) without operating the adaptability calculation of the rule.