Abstract: An apparatus including a grip sensor for controlling the number of revolutions of an engine. The grip sensor detects whether or not fingers of an operator approach toward the grip sensor or the former come in contact with the latter. Usually, the grip sensor is incorporated in the gripping portion of a control lever which controls actuation of working tools. The apparatus includes a controller for outputting a deceleration signal in response to an output signal from the grip sensor in order to reduce the current number of revolutions of the engine to a level lower than the number of revolutions of the engine in the high operative state when no detection is achieved by means of the grip sensor. Alternatively, the controller may output an acceleration signal in response to an output signal from the grip sensor in order to raise the current number of revolutions of the engine to a level higher than that the engine in the idle rotational state when detection is achieved by means of the grip sensor.