A hydraulic driving system includes a hydraulic pump, a driving source, a hydraulic cylinder, a closed circuit hydraulic path between the pump and cylinder, a pump-flow-rate control unit controlling a discharge flow rate of the pump, a flow rate control valve between the pump and the cylinder in the fluid path, a directional control unit, a target flow rate setting unit and a control device. The directional control unit allows a flow of fluid from the pump to the cylinder and prohibits a flow of fluid from the cylinder to the pump when fluid is supplied from the pump to the cylinder via the flow rate control valve. The control device controls fluid flow to the cylinder with the flow rate control valve when the target flow rate is within a prescribed range, and with the pump-flow-rate control unit when the target flow rate is greater than the prescribed range.