HYDRAULIC WORKING MACHINE

[Problem] To provide a hydraulic working machine capable of recovering, as electric power, energy to be used to increase a load on an engine upon burning particulate matter in exhaust gas. [Solution] An exhaust gas temperature raising processing means, which increases a load acting on an engine (2) to raise a temperature of exhaust gas, includes an electric assist motor (5) connected to the engine (2) and an inverter (20) for adjusting a torque of the electric assist motor (5), and also includes a main controller (15) having a first determination means for determining whether or not an actuator control valve (8) is in a non-feed state and a second determination means for determining whether or not clogging has occurred on a filter of an exhaust gas purification system (17). When the non-feed state is determined by the first determination means and clogging is determined to have occurred on the filter by the second determination means, the main controller (15) drives the electric assist motor (5) to generate electric power such that a load acting on the engine (2) is increased.