A load application means, which applies a load to an engine such that a temperature of exhaust gas is raised to a temperature required to burn particulate matter, is comprised of an electric load application means for applying the load to the engine to raise the temperature of the exhaust gas by operating an electric assist motor to generate electric power and a hydraulic load application means for applying the load to the engine to raise the temperature of the exhaust gas by increasing a delivery pressure of a variable displacement hydraulic pump, and a selection control unit is provided for performing control processing to selectively actuate the electric load application means and/or the hydraulic load application means.