To provide an air supplying opening with a mechanism that adjusts the amount of flowing air by changing the air introduction path of the air supplying opening according to the pressure difference between the inside and outside of a room.

In an air supplying opening 1 of a house that passes through the wall surface of the house and consists of a cylinder body for taking outdoor air into a room, an air volume adjustment plate 12 for shielding an air introduction path 5 is provided inside the air supplying opening 1, one end of the air volume adjustment plate 12 is freely rotatably mounted to a rotary shaft being provided inside the air supply opening 1, a spring is mounted at the middle part of the air volume adjustment plate 12, and the opening and closing angles of the air volume adjustment plate 12 can be changed by the spring and wind pressure.