To widen space in an operating compartment and to facilitate constitution of a hydraulic circuit by making it possible to exhaust pilot pressured oil of high pressure without employing a shuttle valve and a pressure sensor.

A flow directional valve 3 is provided with a pilot pressured oil exhausting port 344 which exhausts the pilot pressured oil of the high pressure in either the pilot pressured oil P1 or P2 supplied to pilot ports 315, 316. It makes it possible to be in fluid communication with a pilot port on high pressure side and the pilot pressured oil exhausting port 344 in response to a spool 4 that moves in accordance with pressure difference between the pilot pressured oil P1 and P2 and simultaneously to shut off in fluid communication with a pilot port on low pressure side and the pilot pressured oil exhausting port 344.