PURPOSE: To improve working efficiency in a whole working speed area by increasing excavating speed or horsepower by simple operation to press a button at the time when output of a working machine is not increased.

CONSTITUTION: While a push-button 11 is pressed as required during excavation work, an excavation power up signal is output to a controller 16 for an absorption torque variable valve and a controller 17 for a governor drive device. The controller 16 increases absorption torque of a hydraulic pump 2 by way of outputting an absorption torque increase signal to a solenoid 10a of the absorption torque variable valve 10. Additionally, the controller 17 outputs an injection fuel increase signal to the governor drive device and increases output of an engine 1. To increase absorption horsepower of the hydraulic pump 2, the number of revolution of the engine 1 and absorption torque of the hydraulic pump 2 are reciprocally related and properly controlled.