It is a gas generating suppression device, such as liquefied LNG/LPG, that rehydrates gases generated in the storage tank. The amount of liquid gas in the reservoir is the amount of heat penetrated from the outside, causing some of the liquid gas to evaporate, increasing the pressure in the reservoir. This prevents the internal pressure from rising above the tank design pressure and thus becoming dangerous. The freezer installed on the inside and outside of the storage tank cools the heat exchanger to the set temperature, causing a pressure difference between the heat exchanger and the storage tank, and the rehydrated liquid gas flows back into the storage tank to stabilize the pressure in the storage tank.