PURPOSE: To reduce building site work and improve building efficiency by fixing a square cylindrical frame body in which aggregate is deposited at the outside to the upper deck and sequentially piling up a container-type superstructure unit that is manufactured separately in the frame body.

CONSTITUTION: When the superstructure of the hull is built, a square cylindrical frame body 2 in which a number of types of aggregate are deposited at the outside is fixed to the upper deck 4. A container-type superstructure unit such as a cabin unit 6, public unit 7, galley unit 8, sanitation unit 9, navigation equipment unit 10, etc. for which interior finish work is pre-applied on land is piled sequentially in the frame body 2 from the lower layer section to the upper layer section. As a result, building site work is reduced and the superstructure can be built with good efficiency.