PURPOSE: To prevent liquefied gas from making contact with the upper inside wall of a vessel at a relatively high temperature and thereby prevent generation of a large quantity of gas and its explosion by partitioning a gaseous phase portion of a vessel filled with the liquid into an upper chamber and a lower chamber by means of a partitioning wall.

CONSTITUTION: The gaseous phase portion 5 of a vessel 2 filled with fluid is divided into an upper chamber 22 and a lower chamber 23, and one or more than two communicating holes 24 are formed on a partitioning wall 21 for performing the division. On the other hand, a gaseous phase passage 6 communicating with the outer space of the vessel 2 from the lower chamber 23 thereof is provided and an opening 25 is formed on the gaseous phase passage 6. By the above construction, the partitioning wall 21 prevents the liquid from making direct contact with an upper inside wall at a relatively high temperature in order to suppress generation of a large quantity of gas and quickly exhaust the generated gas to the outside of the vessel 2 through the communicating hole 24, the upper chamber 22 and the opening 25 of the gaseous phase passage 6.