Underground building

The invention discloses an underground building which comprises a top layer structure, a bottom layer structure, a supporting structure and a drainage structure, wherein the supporting structure comprises a first enclosure wall and a second enclosure wall, the first enclosure wall is arranged on the peripheries of the top layer structure and the bottom layer structure in a surrounding mode, the second enclosure wall is arranged between the top layer structure and the bottom layer structure, the second enclosure wall is located in the first enclosure wall, and the second enclosure wall and the first enclosure wall are arranged in a spaced mode and form a first gap; the drainage structure comprises a drainage pipe which is used for draining water in the first gap; and the first gap can gather water leaked from the first enclosure wall, water leaked from the top layer structure and the like, and the water drainage pipe can drain the water. On one hand, the waterproof effect is achieved, on the other hand, leakag