PURPOSE: To obtain a building having a roof simple in assembling and disassembling and good in draining by freely detachably mounting an inclination adjusting means on an upper joist member of a building main body and freely detachably mounting a roof body on an inclined upper face of the inclination adjusting means.

CONSTITUTION: An inclination adjusting means 10 is freely detachably mounted on an upper joist member 11 of a building main body 2 extending substantially horizontally, and a room main body is freely detachably mounted on an inclined upper face of the inclination adjusting means 10. The inclination adjusting means 10 comprises a plurality of adjusting members 14a, 14b spaced apart from each other and each of the adjusting members is provided with the inclined upper face inclined from one end to other end. By this constitution, water on the roof of a building is drained well, and a building can be assembled and disassembled simply.