PURPOSE: To prevent formation of a protrusion protruding outward from a side shell surface, in an opening and closing device for a cover at a side doorway for a loading boat, such as a rescue boat loaded in a ship.

CONSTITUTION: A doorway 2 for a loading boat 4 is formed in a side shell part 1 and a cover 3 for the entrance 2 is matched with the inner peripheral edge of the doorway 2 and closed in such a manner to be positioned flush with a side plate surface. Vertically oblique rollers 7 and 8 making a pair are arranged at the inner arm 6 of the upper end part of the cover 3 and guide rails 9a and 9b capable of guiding the rollers 7 and 8 also making a pair are erected through the doorway 2 slightly near the inside of a ship in such a manner to have guide surfaces positioned facing each other. Inclination guide parts 9a-1 and 9b-1 are formed at the upper ends of the guide rails 9a and 9b, respectively. Since at the initial stage of releasing of the cover 3, the cover 3 is lowered as it is moved slightly forward through the doorway 2, interference with the edge part of the doorway 2 is prevented from occurring.