PURPOSE: To perform the control of a controlled system in accordance with the system state by changing the control parameter in response to the controlled variable set by a control part in a control state of an operating part and setting newly the control parameter at the control part.

CONSTITUTION: The control conditions are initialized, and a test signal generating part 12 transmits the test signals which are held for a fixed time for each 20% opening degree. A control part 9 controls the opening degrees of a valve 8. Meanwhile a parameter calculating part 10 calculates an optimum PI control parameter for the control of the part 9 based on the temperature change information acquired from a temperature sensor 7. The PI control parameter is set at a parameter changing part 11. In a control operation mode, the part 11 monitors the output of the part 9. Then the part 11 changes the PI control parameter at the part 9 based on the relation between the valve opening degree and the PI control parameter and with interpolation/extrapolation of these opening degree and parameter.