An engine revolution speed control device according to the present invention comprises: a hydraulic pump (1) which is driven by an engine (21); a hydraulic motor (4) for vehicle movement which is driven by oil expelled from the hydraulic pump (1) during vehicle movement; an actuator (52) for working which is driven by the oil expelled from the hydraulic pump (1) during the working state; a vehicle driving pedal (6) which during vehicle movement controls vehicle speed according to its amount of operation; a means (33) for speed reduction decision which makes a decision as to whether the amount by which the vehicle driving pedal (6) is depressed is being reduced; and a means for revolution speed control (33). The means for revolution speed control (33) performs normal control by increasing or decreasing the revolution speed of the engine according to the amount by which the vehicle driving pedal (6) is depressed, and, when it is decided that the amount by which the vehicle driving pedal (6) is depressed is decreasing, performs controlled slowing down by reducing the revolution speed of the engine while delaying its reduction amount. And, when during working the engine revolution speed is being adjusted by the use of the vehicle driving pedal (6), controlled slowing down is prevented even when the amount by which the vehicle driving pedal (6) is depressed is decreasing.