PURPOSE: To facilitate execution and shorten the construction period by forming a roof surface by supporting the top parts of a roof consisting of roof panels each other, having an opened port part interposed.

CONSTITUTION: A roof panel 1 is formed of battens 2 such as asbestos cement plate and a frame member 3 which is formed by joining the outer peripheral edge part on the reverse surface into a frame shape. Then, a joint metal fitting arranged on a pole plate and a joint metal fitting of the panel member 1 are meshed, and supported to each other on the top part side of the roof by tilting each panel member 1, and a roof surface is formed. The first covering member is installed at the opened port part at the roof top to prevent leak of rain water. Further, a through member 8 is installed at the joint part of the panel member 1, and the upper opened port part is covered by the second covering member 9 to prevent intrusion of dust. Accordingly, the need of a roof-truss at a garret is obviated, and execution work can be simplified.