To provide a dome structure preventing the production of excessive stress in the flange of a tank dome in a liquefied gas tank.

A part between the flange 10 and a hull 1 extending outside in the horizontal direction from the upper end of a warehouse port 5 of a liquefied gas tank body 3, is connected by bellows 9, and by forming a lower warehouse port 5a and an upper opening warehouse port 5b while having a recessed top plate 11 for blocking the warehouse port 5 in a lower side position more than the flange 10, the occurrence of a large temperature difference in the flange 10 can be prevented, preventing the production of the excessive stress.