A liquefied gas tank installed in a surrounding structural body includes: a tank main body in which a liquefied gas is storable, the tank main body including a plurality of planar portions and corner portions between the planar portions, the corner portions having less rigidity than that of the planar portions; a bottom supporting body that supports the tank main body from below the tank main body; and a plurality of side supporting bodies that support the tank main body from side of the tank main body. The tank main body is configured to stand by itself by being supported by the bottom supporting body when the tank main body stores no cargo, and be supported by the bottom supporting body and the side supporting bodies when the liquefied gas is stored in the tank main body.