PURPOSE: To increase the rigidity against a force acting upon the upper surface of a gunwale member by forming a swollen part on the upper surface of a deck outer peripheral part along the ship side at a suitable inteval and supporting the gunwale member by the swollen parts.

CONSTITUTION: A swollen part b1 is formed on the upper surface of the outer peripheral part of a deck b, and is formed integrally with the deck b. Accordingly, the sollen part b1 is protruded correlatively from the inner wall of a bulwark a1 into the ship, and a staged part 2 is formed at the intermediate of the protruded part, the lower end of the fitting part c1 of the qunwale member c being supported at this part. At the joined part of the bulwark a1 and the gunwale member c there is fitted a fender d, and the upper surfce of the fender d is formed on a surface same as that of the gunwale member c, the upper surface of the gunwale member being formed widely. By this organization, the gunwale member is supported by the swollen part through the fitting part, thus the rigidity of the gunwale part being increased.