To provide a hydraulic driving device capable of preventing an engine stall by an engine overload, by reducing a load of an engine by controlling a delivery oil quantity of a hydraulic pump with a simpler and more inexpensive constitution than a conventional constitution.

This hydraulic driving device includes a pump control device 150 for controlling the delivery oil quantity by changing capacity of a hydraulic pump P. This pump control device 150 includes a servo piston 151 for changing variable capacity of the hydraulic pump P by using delivery oil pressure of the hydraulic pump P and a pilot pump 70 as capacity control oil pressure, and a variable throttle valve 155 arranged in an oil passage 97 connected to an oil tank T by branching off from an oil passage 96 for guiding the delivery oil pressure of the pilot pump 70 to the servo piston 151 as the capacity control oil pressure and adjusting the capacity control oil pressure by adjusting a pressure oil flow rate flowing to the oil tank T by opening-closing the oil passage 97 in response to operation input of a worker.