To provide a mechanism for preventing noise generation in a vent tube in a gas station, especially for preventing the generation of an aeolian tone, etc. caused by the unstable behavior of a valve mechanism.

The valve mechanism of a vent tube is so formed that a vent valve main body 3 usually closing a vent hole 2 opens the hole 2 by the pressure increase in a tank. A vibration damping mechanism is placed at a position where a noise is generated by the unstable behavior of the valve mechanism. For example, a wire rope 11 connects between the main body 3 and a vent valve support body 1 supporting the same.