Provided is a mechanism for connecting a valve and a joint, which is used in air piping and which connects a tube to the housing 2 of the valve through the joint 1. The housing 2 of the valve has formed therein a connection hole 22 in which the joint 1 is inserted for connection. The connection hole 22 has a snap ring fitting groove 23 in the inner peripheral surface thereof. The joint 1 has formed in the outer peripheral surface thereof a snap ring receiving groove 31. In a state in which the joint 1 is inserted in the housing 2, a snap ring 3 in the receiving groove 31 is fitted and located in the fitting groove 23.