PURPOSE: To enhance the practical value of a function improving device for a finger, by providing a pipe joint to an air supply and discharge hose and mounting a valve for closing a flow passage in the socket or plug on the side of a main body and providing a flow rate control mechanism.

CONSTITUTION: When the rotary cylinder 77a on the side of a plug 75a is re volved in such a state that the socket 85a, and plug 75a provided on an air supply and discharge hose 62 are connected, the projection 96 of a flow rate control disc 94 revolves within the range movable in a guide groove 92 and the opening quantity of a flow hole becomes max. at an angle of rotation allowing the fan-shaped punched hole 91 of a rear member 90 to coincide with the fan-shaped punched hole 95 of the flow rate control disc 94 and becomes zero when the fan-shaped hole 95 is closed by a flat surface 93. Therefore, a flow rate is variably controlled from zero to a full-open flow rate. When the socket and the plug are separated, the slide valve 83a for the control of a flow rate provided on the side of the plug 75a is pressed by the elastic force of a spring 87a to close a flow passage and a fluid is blocked and the closed state is kept until the socket and the plug are connected.