An inference method and an inference apparatus for use with a knowledge base system and knowledge base system supporting method and apparatus using the inference method and apparatus wherein there are employed rules each being comprised of a set of (1) a condition description part including a condition stipulating a plurality of states of a frame representing an object and constituting an object world of at least one pair of a slot and a value thereof and (2) an operation description part stipulating an operation to be executed when the condition is satisfied. For an inference processing, a rule for which a condition of its condition description part is satisfied is executed according to an operation described in the operation description part. A condition judging sequence is specified for satisfaction of a condition for each frame of the condition description part of the rule. It is also specified whether or not information related to a processing result obtained from a condition judge processing on each said frame is stored in a memory. Condition judgements are achieved for satisfaction of conditions respectively associated with the frames of the condition description part according to the specified sequence based on the processing results in the memory, thereby conducting a reasoning operation.