PURPOSE: To accurately position roof panels in the direction of a gable when connecting the roof panels together in the direction of a line connecting eaves to a ridge.

CONSTITUTION: The panel frame 1 of each roof panel has a plurality of long vertical frames 5 provided in parallel to one another along an eaves-to-ridge line, so that the roof panels are connected together. In the panel frame 1 of either an eaves side roof panel A or a ridge side roof panel Aa, vertical frames 5b except those on the gable side are shifted in the direction of the gable by the thickness of each vertical frame 5b. Each of the shifted vertical frames 5b is brought into contact with the side face of the vertical frame 5 of the other panel frame 1 and inserted into the panel frame 1 and the vertial frames 5 on the gable side are assembled by butt joint.