To reinforce earthquake resistance in a relatively short construction period without removing a rectangular plane roof tile part in an existing ridge structure constructed by a large winding fastening method.

(1) A ridge roof tile temporarily removing process: A fastening wire 23 of a ridge structure constructed by an existing large winding fastening construction method is released, and a ridge tile 22 of the uppermost part is removed once. (2) A ridge tile installing member installing process: A metallic plate material 3 for covering an upper surface 21a and a side surface 21b of the plane roof tile 21 is arranged in the lengthwise direction. Installing metal fittings 4 having a square U-shaped cross section are arranged in a plurality on this metallic plate material 3, and these metal fittings are fixed by a screwing-in nail 43 reaching up to a purlin 5. Next, square columnar wood 6 is fitted in these square U-shaped installing metal fittings 4, and is fixed by a screw 61 from a side surface. (3) A ridge tile rearranging process: The removed ridge roof tile 22 is placed again in the uppermost part, and is fixed to the square columnar wood 6 by a screwing-in nail 22a.