PURPOSE: To effectively and quickly carry out an inference by outputting the result of inference as a control signal.

CONSTITUTION: An inference schedular part 1 inputs the event value information given from an approximate inference executing part 4 and the knowledge information given from a knowledge storage means 9 and outputs the result of inference. Then the result of inference is outputted by a conclusion control part 3 as a control signal which is outputted to an external equipment for its control. In such a constitution, a multi-stage inference using plural knowledge bases can be carried out. Furthermore the inference is effectively and quickly carried out.