PURPOSE: To remarkably decrease noise of an engine by maintaining a throttle lever in its high idle position when an engine is approaching to its no load condition and outputting a command signal for maintaining a high idle cut rotational speed when a throttle lever is in its high idling position and the rotational speed is increased to its high idle cut rotational speed.

CONSTITUTION: A detection signal from a potentiometer 13 is inputted to a controller 11' when the throttle lever 14 of a throttle device 12 is operated in a specified direction. A command signal based on the detection signal is outputted to a governor 2' via a control motor 15' by the controller 11'. As a result, the rotational speed of the engine 1' is controlled. In this case, high idling cut rotational speed lower than the high idling rotational speed of the engine 1' is preliminarily stored in the memory 21 of the controller 11'. Meanwhile, when the throttle lever 14 is in its high idling position and the rotational speed is increased to the high idling cut rotational speed while the engine 1' is approaching to its no-load condition, a command signal for maintaining the state is outputted.