PURPOSE: To prevent a valve part of a valve rod from being worn or scratched, by interposing a manipulating thread member rotatably fitted on the peripheral barrel part of the valve rod and threadedly engaged with a female part of a joint body so as to extend and retract the valve rod axially of the joint body, between joint body and the valve rod.

CONSTITUTION: A manipulating thread member 21 rotatably fitted on the peripheral barrel part 20 of a valve rod 6A and threadedly engaged with a female thread part 10A of a joint body 1A so as to extend and retract the valve rod 6A, axially of the joint body 1A is interposed between the joint body 1A and the valve rod 6A. When the manipulating thread member 21 is turned in one direction, the valve rod 6A is retracted directly from a fluid communication hole 3 without revolution, through the intermediary of the manipulation thread member 21. Then, fluid 25 flows into the female thread part 5 of the joint body 1A, and flows at first into a fluid inflow hole 12 before it flows into a fluid discharge hole 9A. Thus, it is possible to prevent the valve part of the valve rod from being worn or scratched during sealing of the fluid communication hole.