To safely, positively carries out actuation, including steering, turning movement at an appropriate speed required in the entire travelling speed region.

Each of hydraulic control systems, 15A, 15B, 15C has a hydraulic pump 17 independently provided aside from a hydraulic pump driven by means of an engine for travel or the like, and reversely, axially driven by means of an electric motor 16, and an electromagnetic directional control valve 18 selected for supplying oil to a hydraulic cylinder 36 from the hydraulic pump 17, and for discharging the oil from the hydraulic cylinder 36. All or part of a plurality of the hydraulic control systems supplies and discharges oil to and from the hydraulic pump 36 through a manifold block.