PURPOSE: To constitute this controller so that an expert system developer can execute an inference of a high level by selecting plural inference systems and combining them freely by leading in inference control information which does not depend on an inference system such as a controller, an event and a queue.

CONSTITUTION: The part for executing an inference system and the part for controlling the inference system become separate devices of an inference system executing device 1 and an inference system controller 3, respectively. An inference system control means 34 of the inference system controller 3 determines an event to be executed from a queue storage part 33 in which an execute sequence of an event is stored, in accordance with control information related to the whole inference of a controller storage part 31, and fetches an execution code from an event storage part 32. This execution code is delivered to an inference system executing means 12 and a rule group or a function group is actuated, and generation of a solution is executed. The generated solution is delivered to a user interface device 2 through an inference system control means 34, and brought to output display. In such a way, an expert system developer can execute an inference of a high level by selecting plural inference systems and combining them freely.