To provide a valve for automatic air supply capable of materializing an automatic air supplying system by using a general tire.

A relief valve mechanism 91 opens when internal pressure of a gas passing route 34 becomes larger than a specified value and can hold pressure in a tire 14 at the specified value or less. It is possible to supply gas to the inside of the tire 14 by a pump separately provided from the vehicle when it is required to charge gas to the tire 14 in a parking state. At this time, it is possible to charge gas to the tire 14 through a check valve mechanism 90 of the valve 30 for automatic air supply in a state where an air supply pipe 16 remains connected to a tire valve 15, and consequently, it is possible to materialize the automatic air supply system by using the general tire 14 having only the tire valve 15 as a charging port of gas.