PROBLEM TO BE SOLVED: To improve transportability of a roof material in the present invention.SOLUTION: A construction method of a roof comprises a rail laying process, a pedestal adjustment process and a roof material transport process. In the rail laying process, a lower rail 30L and a high rail 30H higher in a height than the lower rail 30L, are laid in parallel on the roof 10A. In the pedestal adjustment process, a carriage 50 capable of adjusting a height of a pedestal 58 for placing a folded-plate 20, is respectively installed on the lower rail 30L and the high rail 30H, and the height of the pedestal 58 is adjusted between the carriages 50. In the roof material transport process, the folded-plate 20 is transported by respectively moving the carriage 50 along the lower rail 30L and the high rail 30H in a state of extending the folded-plate 20 between the height-adjusted pedestals 58.
