PURPOSE: To return a fuel injection amount adjusting member to a non-injection position precisely by operating force generated by a hydraulic piston when stop of a diesel engine is necessitated.

CONSTITUTION: Under a normal condition, a fuel injection amount adjusting member 4 for adjusting a fuel injection amount is moved to an injection amount adjusting position by an actuator driven by an outer signal. When it is in an emergency condition, the fuel injection amount adjusting member 4 is moved to a non-injection position by oil pressure of an oil pressure chamber 6 forcibly. Namely, the fuel injection amount adjusting member 4 is moved to the non- injection position by operating force generated by rising of pressure in the oil pressure chamber 6, and then, after an engine is stopped in association therewith, pressure in the oil pressure chamber 6 is reduced. When the rotational number of an engine reaches the level of 0 completely, electrification of an electromagnetic valve 13 is disconnected, and the flow passage of operating oil is sealed. After that, operating oil remaining in the oil pressure chamber 6 is returned to an oil reservoir chamber 10 by an oil returning passage 15 passing a restriction 14.