Provided is a working machine capable of decreasing a voltage of a DC busbar (DC bus) with a configuration suppressing a degradation in reliability. A hybrid type construction machine as a working machine includes: a DC bus which is connected to a rotation motor via an inverter circuit, a battery which is connected to the DC bus via a step-up/step-down converter and a switch, a controller which drives the inverter circuit and the step-up/step-down converter, a cooling liquid circulating system which includes a pump motor, and an inverter circuit which is connected to the DC bus and driving the pump motor. The controller includes a mode used for decreasing the voltage of the DC bus, and in that mode, the switch enters a disconnection state and the inverter circuit is operated to consume electricity in the pump motor.