Disclosed is a vessel having a storage tank for storing liquefied gas therein. The vessel comprises: a boil-off gas heat exchanger which cools the boil-off gas discharged from the storage tank; a compressor which compresses a part of the boil-off gas discharged from the storage tank; a spare compressor which compresses the other part of the boil-off gas discharged from the storage tank; a propulsion compressor which compresses the boil-off gas supplied to the boil-off gas heat exchanger; a refrigerant heat exchanger which additionally cools the cooled boil-off gas; a refrigerant decompression device which expands the boil-off gas cooled by the refrigerant heat exchanger and resends the expanded boil-off gas to the refrigerant heat exchanger; and a first decompression device which expands the boil-off gas cooled by the boil-off gas heat exchanger and the refrigerant heat exchanger. Thus, the present invention improves the re-liquefaction performance of the boil-off gas.
