To shorten the time required in repairing, in repairing a thin-walled part or void generation part of a reaction injection-molded object, by filling a part to be repaired with a photosetting adhesive to cure the adhesive with the irradiation with light and finishing the cured adhesive into a predetermined shape.

The void generation part or thin-walled part of a reaction injection-molded object 1 being an RIM(reaction injection molding method) molded article comprising a dicyclopentadiene resin is set to a part 2 to be repaired and, in order to improve the adhesiveness of an adhesive to the part 2 to be repaired, the surface of the part 2 to be repaired is treated with sand paper to be roughened. Next, the part 2 to be repaired is filled with a photosetting adhesive 3 so as to become a built-up state, the photosetting adhesive 3 is irradiated with curing light from a light irradiation device using a high pressure mercury lamp or a metal halide type high pressure mercury lamp to be cured and finished into a predetermined shape, and a necessary coating 5 is applied to the whole of the molded object 1 to complete a reaction injection- molded product.