The present invention has no such assembled or coupled upon a separate connection member and the connection frame required between the plurality of unit hull, by introducing a simple and convenient new bond structure instead of a number of bolted assembly and and disassembly is easy, a plurality of units of the hull to connect to on the prefabricated expandable barge that can be used to expand the variety of shapes, a plurality of units of the hull is assembled by mutual locking means in the assembled extended barges coupled expansion, is, before and after a long elongated body and the unit hull, respectively, and , over the front insert formed depressions along the right and left longitudinal direction of the left insertion protrusion protruding along the front-to-rear longitudinal direction on the left side of the body, and the right insertion groove on the right side of the body formed depressions along forward and backward longitudinal direction, said body groove and protruding from the right and left along the longitudinal direction on the rear surface of the body rear portion inserted stone Box, and the unit of the hull, each, adjacent the other left side insertion of the unit hull at the right insertion groove of days hull projections or rear insertion stone portion is inserted after the assembly by the locking means extended combined or days left inserted in the hull projections adjacent another unit right insertion of the hull in front insertion groove or the groove after insertion portion is characterized in that the extensions are coupled together by the locking means.