PURPOSE: To make it possible to form a valve duct equivalent in effective section area to the fluid pipe by providing the central area with a globular valve equipped with a circulation orifice equivalent in effective section area to the fluid pipe and inside of a socket with a board spring to move the valve rotationally.

CONSTITUTION: A valve 2 is globular, in its center equipped with a circulation orifice equivalent in effective section area to the fluid pipe and a board spring 3 is latched. When a plug 15 is connected into a socket 1, the valve 2 is pressurized by the plug main body 16 causing the board spring to elongate and the valve 2 to move rotating. When the valve 2 rotates at the right angle, the circulation orifice performs the duct interconnection of the socket 1 and the plug 15. The valve duct of the automatic valve 19 of a quick disconnect coupling is equivalent in effective section area to the plug 15 and has no protrusion; accordingly, friction loss or pressure loss of fluid can be controlled.