To provide an intake valve which suppresses damage to the minimum even if there is leakage, and is stably used with the lapse of time.

In case of leakage from a main vale 5, the water leakage to the outside is automatically forcibly shut off by the action which a holding member 13 or an expansion agent is made so as to prevent permeating due to the ingression of high humidity atmosphere by providing the shut off valve 19 at the intake port 18 during normal time, is flooded and changed. An appearance is changed by the movement of a valve storage chamber 9 or a sub valve 12 so as to be able to confirm abnormality.