PURPOSE: To easily carry and dismount materials and freely set the floor area by providing a first enlarged part including a movable floor which can be drawn out and stored, a movable side wall and a movable roof outside both end open areas from a fixed part, and providing an expansible elongation and contraction wall for forming a second enlarged part.

CONSTITUTION: A movable floor, a movable side wall 8 and movable roofs 10 are drawn out from the interior of a fixed part 1 to form a first enlargement part. Subsequently, rotary roofs 6 and rotary floors fitted to the first enlargement part are unfolded and kept substantially horizontal and expansible side walls 11 and expansible block walls 12 folded up in the first enlargement part are drawn out to form a room space of a second enlargement part 13. In this case, guide rails for guiding and supporting the movable floors and the rotary floors are arranged side by side with the fixed rails for supporting the fixed floor to conduct the works. Thus, the volume and the floor area can be quickly and easily enlarged in a temporary place, and carrying and dismounting can be easily handled.