PURPOSE: To provide the controller to control the respective parts of an electrophotographic process in a copying machine or the like.

CONSTITUTION: This controller has an operation value decision part 6 inputting the output values of various sensors 3 installed at the charge/image exposure/ development/transfer/fixing parts of the copy machine or the like and a control value to a control object, preparing and holding a control rule beforehand for deciding the manipulated variable of a controller at a control part 4, and deciding the operation value of the controller according to the current output values of respective measuring instruments; the antecedent part consequent part of the above-mentioned control rule are fuzzy rules defined as a membership function in fuzzy theory, as the deciding method of the operation value, the output values of the respective measuring instruments are made fuzzy and imparted to the antecedent part of these fuzzy rules, in this case, the fuzzy value of the consequent part is calculated to all the rules and by using a fuzzy inference system such as a min-max-center of gravity method or an algebraic product- addition-center of gravity method, etc., the final operation value is decided.