To provide a faucet, equipped with a check valve having a water hammer relaxing mechanism capable of reducing water hammer noises generated, when preventing the feed of a back-flowing water onto the upstream side.

A valve seat member 11, having a through-hole 10 in the direction of a flow passage and being movable toward the flow passage, valve seat energizing mean 12 for energizing the valve seat member 11 to a downstream side, a valve element member 13 for abutting the valve seat member 11 from its downstream side to block the through-hole 10 at its end, a guide portion 14 for guiding the valve element member 13, and valve element energizing means 15 for energizing the valve element member 13 to the upstream side are provided in an almost cylindrical housing 16.