PURPOSE: To improve deck room fitting work performance and reduce vibration propagated to the deck room from an engine room by supporting the deck room only by supports erected on the hull.

CONSTITUTION: An independent deck room 4 is supported on the hull 2 only by several supports 5 erected on the hull 1. The deck room 4 is produced on the ground separately from the hull 1 and then fitted to the supports 5 on the hull 1 by bolts, nuts, and the like. Outfitting work workability is thereby improved by far, and the vibration of the wall panel of an engine room 3 generated by excitation from a main engine, auxiliary machinery, and the like in the engine room 3 is not directly propagated to the deck room 4 so as to reduce noise in a living quarter in the deck room 4, a pontoon bridge, and the like. When the hull is deformed by longitudinal vibration out of hull vibration, the supports 5 are deformed but the deck room 4 is not deformed, so that the longitudinal vibration of the deck room 4 is reduced.