PURPOSE: To bond the faying faces of an inner and an outer hulls positively with an adhesive regardless of the forming error of the inner and outer hulls at the time of manufacturing a hull of double layer structure.

CONSTITUTION: An inner and an outer hulls 2, 3 are fitted after applying adhesive 6 to the respective faying faces. Air in a cavity part 7 between both hulls 2, 3 is then evacuated, and the faying faces are pressure-welded to each other by the inner-outer air pressure difference.