PURPOSE:To improve the responding property and the controlability of the engine speed by a method wherein a control pulse width operating circuit, operating the objective control amount of an actuator, and a stop time operating circuit, operating the stopping time of driving of the actuator, are provided in the device. CONSTITUTION:The control pulse width operating circuit 7 outputs a difference between the outputs of the objective engine speed operating circuit 5 and an engine speed operating circuit 4. The stop time operating circuit 17 inputs an ignition time interval date, outputted by a frequency measuring circuit 3, and outputs it to a stop time counter 16. The stopping time of driving of the actuator is changed in accordance with an operation parameter indicating the time of de- lay of responding of the engine. Thus, the most proper and the shortest stopping time of driving may be obtained and the overshoot of the engine speed may be prevented.