To form a vent hole in the outer wall of a building while keeping moisture proof sheets air-tight.

A vent pipe is formed of a vent hole through the outer wall of a building with moisture proof sheets 6, 7. A vent pipe 21 has a flange 23 overhung from the peripheral face of a pipe 22 to an approximately vertical direction to support the pipe 22 at a specified position, where the vent hole is formed, and ensure air-tightness between the moisture proof sheet 7 and the peripheral face of the pipe. The vent pipe 21 and a flange material 24 which were separately provided in the past are made into one unit to prevent the dislocation of the pipe 22, when mounted on an outdoor hood, resulting in less air-tightness between the pipe 22 and the moisture proof sheet 7 (the flange 23).