A valve for a gas cylinder consisting essentially of a valve body provided with a valve chamber containing a valving element which opens and closes an annular valve seat, and a gas cylinder plugging end portion and a pipe-connecting port both formed on the valve body. The gas cylinder plugging end portion contains an upstream side gas channel communicating at one extremity to an end thereof and at the other extremity to an internal circumference of the valve seat. The port contains two downstream side gas channels each opening to an end thereof and at the other extremity to an external circumference of the valve seat. A metal connector can be fitted in the port. The metal connector contains two channels connected to the two downstream side gas channels respectively. Valve chamber openings of the downstream side gas channels are located to oppose each other across the valve seat.