The invention achieves a good engine speed control without increasing a cost and a lowering a reliability of an apparatus in a general purpose engine. In a rotating speed control apparatus of an engine in which an electronic control unit (10) controls an engine speed by operating so as to open and close a throttle valve (40) by an electronic governor apparatus (4) on the basis of an engine speed detected by a crank angle sensor (7) corresponding to an engine speed detecting means and regulating an intake air amount, the opening and closing operation of the throttle valve (40) in the electronic governor apparatus (4) is carried out by a rotating force of a motor rotationally driven only in one direction and an elastic repulsive force of a return spring energizing in a reverse direction.