PURPOSE: To easily detect the position of a supply quantity adjustment member without using a position sensor of ultrahigh accuracy in order to correctly control the injection quality by correctly controlling the fuel supply.

CONSTITUTION: An actuator 9 for setting the fuel supply quantity of an automobile is adjusted in an output adjustment zone of an internal combustion engine comprising a controller to which a target value and an actual value are supplied to change a position of the actuator and to from the control deviation. A sensor 12 relative to the actuator detects the velocity (v) or acceleration (b) of the actuator, and a position signal (x) indicating the position of the actuator is formed on the basis of this sensor signal by using an observer 16. As the velocity or acceleration of the actuator is detected, an expensive position sensor of high resolving power becomes unnecessary.