To enable the use of crane while eliminating the residual sediment in a hold after throwing away the sediment by forming a top surface of the center beam into a triangle oblique wall body at the time of using a vessel as a bottom-hopper barge, and forming a bottom part of the hold flat and horizontal at the time of using the vessel as a box-shaped sediment carrying vessel.

An oblique wall body 21 is formed of a pair of movable oblique wall bodies, and at the time of using a vessel as a bottom-hopper barge, the right and left oblique bodies 21 are made to abut on each other on the center beam 19 so as to have a nearly triangle cross section, and at the time of throwing away the sediment in the hold into the sea, a bottom door 17 is opened so as to prevent the generation of residual sediment in the hold. At the time of using a vessel as a box-shaped sediment carrying vessel, the oblique wall body 21 is divided into two, and respectively housed in a recessed part 20 formed by the bottom door 17 and the center beam 19, and the bottom of the hold is formed flat and horizontal so that the work by crane is easily and quickly performed.