Provided is a working machine having a closed circuit system provided with a flushing valve which provides good operational characteristics even when the direction of a load on a single-rod cylinder is reversed, which is compact, and which accommodates a high flow rate. A flushing valve is provided with: a valve body; a spool making it possible to select, depending on the position of the spool within the valve body, whether to connect a first flow passage and a third flow passage, to connect a second flow passage and the third flow passage, or to block the connection between the first flow passage, the second flow passage, and the third flow passage; a first liquid chamber provided within the valve body and allowing hydraulic oil from the first flow passage to flow therein; a first pistonfor pressurizing the hydraulic oil, which has flowed into the first liquid chamber, and moving, by means of hydraulic pressure within the first liquid chamber, the spool to the position where the second flow passage and the third flow passage are connected; a second liquid chamber provided within the valve body and allowing hydraulic oil from the second flow passage to flow therein; and a second piston for pressurizing the hydraulic oil, which has flowed into the second liquid chamber, and moving, by means of hydraulic pressure within the second liquid chamber, the spool to the position wherethe first flow passage and the third flow passage are connected.