PURPOSE: To make roof height changeable whenever necessary so as to deal with multipurpose applications with efficacy by connecting the divided parts of a roof-forming structure at their inside ends, and supporting the outside ends of the divided parts in such a manner as to be freely vertically rolling and freely moving inside and outside of the building.
CONSTITUTION: A roof-forming structure 3 is divided into a plurality of structural parts 3A, 3A, the inside ends of which are connected together in such a manner as to be freely rolling relative to each other. The outside end of each part 3A is supported to a fixed portion Fx in such a manner as to be freely vertically rolling relative to the fixed portion Fx and capable of free relative motion inside and outside of the building. The outside end of each structural part 3A is repositioned by slide drive gears 10, 10 toward the inside or outside of the building and is held in position. The structural parts 3A are suspended and supported by winches 11, 11 and are vertically rolled or held in position. The height of the roof top portion of the structure 3 is changed as needed according to purposes.