PURPOSE: To perform precise control by precisely predicting a manipulated variable irrelevantly to the control mode of a low-order system.

CONSTITUTION: This system is equipped with a decentralized control system including plural PID control means 2101-210n which have plural control modes respectively, find manipulated variables for controlling the controlled variables of controlled systems by PID arithmetic, and controls the controlled system according to the manipulated variables and a model predictive control means 100 which reads the respective control modes and control information of the PID control means 2101-210n out at a specific control period, predicts controlled variable future values of the controlled systems on the basis of the read control modes and control information by using dynamic characteristic models of the controlled systems and also sequentially calculates mutually relative manipulated variables of the PID control means 2101-210n so that evaluation functions regarding the deviations of the predicted controlled variable future values from the previously given controlled variable commands and the manipulated variables become minimum, and sends out the calculated manipulated variables to the corresponding PID control means as set values according to the control modes.