PURPOSE: To enhance control accuracy by transmitting an ascending and descending control signal from a control side and operating a controlled device only during operating time which is obtained by a difference between a target value to be set and a current operation value of the device to be controlled selected by the control side.

CONSTITUTION: A controlled device selection signal is inputted in a control operating board 1, device selection is translated 10, and a device to be cotrolled 7 is specified. A current operation value of said device 7 is converted 8, and inputted into an information processor 14. With the difference between the current operatiion value and a target value to be set, ascending or descending operating time is obtained. Then an operating signal is translated 16, and a clock signal 19 conducts an ascending or descending gate 17 or 18. Finally a delay timer 22 is set to said operating time which is inputted into a set point memory unit 20. A comparator 21 obtains the difference between a set point of the memory unit 20 and the current value 8, and a controller 6 is managed so that this difference is eliminated. In this way highly accurate control free of hunting can be executed.