To reduce the field man-hours, in the structure for preventing the entry of condensed water or the like into a cabin, by eliminating the coaming members that have been especially hitherto watertightly and continuously welded on a deck.

To the base member 12 for covering the lower end periphery of a wall member 10 that forms a cabin 4 on a deck 2, a sealing material 15 for maintaining the watertightness in the joint with the deck 2 on the hull outer plate 1 side as the hull steel plate is applied to prevent the intrusion of condensed water on the outer plate 1 into the cabin 4. Thus, the coaming that has been hitherto watertightly erected on the deck 2 by means of continuous welding between the wall member 10 and the hull outer plate 1 can be dispensed with, so that the field man-hour can be reduced.