PURPOSE: To provide an inference control method for an expert system capable of performing scrupulous inference control and inference with high efficiency.

CONSTITUTION: A peripheral process 10 is provided with a state change detecting function 11, a table detecting function 11 classified by every inference, a judging function 13 classified by every inference, an inference start request mail transmission function 14 and a retrieve function 15 classified by every inference, and also, the scrupulous inference control can be executed by an inference process 20 by providing an inference start request mail receiving function 21 and corresponding inference functions 22a-22n classified by every specification.