PURPOSE: To prevent a bleeder screw from being easily damaged by foreign matter such as flying stones or the like by screwing a large contour part of the bleeder screw to the large bore part of a bleeder hole and positioning a reference surface of the bleeder screw in the large bore part in a condition that a valve unit is seated.

CONSTITUTION: First at the time of air bleeding work, a different-shaped section part 4a of a tool 4 is inserted to a different-shaped hole 3d of a bleeder screw 3 placed in a valve-closing condition with a valve unit 3c seated in a valve seat 2c, and the screw 3 is slightly screwed out by rotating a grip part 4b by 1/2 to 1 turn. Here one end of a hose 5 is previously connected to a hose connection part 4c in an end part of the grip part 4b with the other end part left as inserted to the vessel, and in this condition, a brake pedal is stepped in. In this way, an operating flow of fluid, containing air in a liquid pressure circuit in a hydraulic equipment main unit 1, is introduced to the deformed hole 3d after passing through a space between the valve seat 2c and the valve unit 3c from a small bore hole 2d, and the fluid is allowed to flow in a through hole 4d from the top end face of the deformed section 4a of the tool 4 and discharged in the vessel through the hose 5 from the hose connection part 4c.