PURPOSE: To enable cargo handling to be performed in high efficiency with a mast folded in a direction with no interference, when the cargo handling is performed, by arranging a cargo hatch of circular shape or oval shape and the like just below the foldable mast in a bulk cargo ship equipped with a sail.

CONSTITUTION: In a procedure of folding a mast, lines 9, 10 are provided in a suitable part in the upper of the mast, and a pin, connecting the bottom part of a strut 1c in a stern side to an upper connection part 3 of a dispersed strut 2 just below the strut 1c, is extracted. The line 9, provided in the suitable part in the upper of the mast, is guided to a winch, and winding the rewinding line 10 of the line 9, the mast is tilted to the front. Here in a stage before the mast is tilted and folded, an eye 12 on a circular hatch cover 4a is left as connected to the eye 12, provided in the bottom of the rear side strut 1c, through a block by the line. Then the mast to be folded, resulting in obtaining a counterweight in an opposite side to a supporting point, can be smoothly folded, when the mast is folded, a hatch is placed in an opened condition enabling cargo handling to be performed.