PURPOSE: To provide a load pressure sensing flow rate governing valve wherein operation oil is mechanically adjusted in its flow rate in accordance with the load pressure to be applied to an actuator and a hydraulic grinding stone expansion device for a honing machine having the valve.

CONSTITUTION: A flow rate governing spool 20 is controlled in its axial position where pilot pressure caused by operation oil on the side of an outlet port 33 and spring pressure of a pressure setting spring 21 are balanced. An opening area of a variable throttle 55 is adjusted. A hydraulic pressure on the side of the outlet port 33 is mechanically and automatically set to be the value which is set by the pressure setting spring 21. In addition, a flow rate of the operation oil is adjusted to be a set value. A grinding stone device for a honing machine utilizes such a load pressure sensing flow rate governing valve. In such a device, hydraulic pressure inside a pressure chamber in a hydraulic cylinder which moves a cone rod in an axial direction is adapted to the pilot pressure.