To stabilize a non-self-adjusting process or closed-loop unstable process by calculating a predictive control variable corresponding to an operated variable and increasing the value of the operated variable based on the difference between the predictive control variable corresponding to the operated variable and a set value, and sensitivity.

An external loop controller 10 adjusts an external loop set value r(t)18 to generate internal loop set value r'(t) 24, and an internal loop controller 12 outputs an operated variable u(t) 30 and an optimum prediction time k(t) 22. The operated variable u(t) 30 is supplied to a downstream controller 14 and outputted as a value 34 to be transferred to a process 16. When the downstream controller 14 limits one of operated variables 30, a logic signal 20 indication this limitation is outputted from the downstream controller 14 and supplied to a restraint processor 35. The restraint processor 35 outputs a signal 32 showing response to the limiting operation to the proper external loop controller 10.