PURPOSE: An LNG storage tank is provided to reduce manufacturing costs by forming a fluid passage in a coffer dam without increasing the amount of equipment for discharging LNG. CONSTITUTION: LNG storage tanks are arranged in a floating marine structure with coffer dams(115) in two lines. The coffer dams longitudinally divide the inner space of the LNG storage tank and reduce sloshing. The LNG storage tank has a lower fluid passage. The lower fluid passage is formed in the bottom of the coffer dams. LNG is moved between the LNG storage tanks through the lower fluid passage.
