Coupler

A female coupler comprises a valve support accommodated in a hole portion of the injection port and comprising a projecting portion having a axial hole, a cylindrical coupler main body placed around the projecting portion and comprising a locking projecting portion on an inner peripheral surface, a part of the main body being embedded in the injection port so as to have its position fixed, a base valve accommodated in the main body and having an fitting insertion portion inserted into the axial hole and a valve seat portion placed on the projecting portion, the fitting insertion portion and the valve seat portion being connected together, a bar-like portion projected from the valve seat portion and having valve grooves formed on a peripheral surface, and an deformable packing member placed on the valve seat portion and accommodating the bar-like portion, the packing member being fixedly retained in the main body.