To obtain an economical hull structure by employing an independent prismatic tank having a large tank volume with respect to a ship size and reducing material cost.Provided is a LNG ship or a LPG ship having a structure in which a substantially prismatic tank is installed inside a hold while not being integrated with a hull structure material, wherein the tank is a long tank 30, which has a larger dimension of a ship longitudinal direction than that of a ship width direction and is installed inside the hold along a ship longitudinal direction, and the long tank 30 is divided into two or more liquid cargo compartments 30-1, 30-2, 30-3 in the ship longitudinal direction by one or more bulkhead plates 31, each of which is formed in the ship width direction as one plate.