To reduce a cost and improve workability in a rebuilding method for a building in which an opening section is formed to an existing wall panel for the building.

The method for rebuilding the building contains an opening- section forming process in which the opening section is formed between vertical frame materials 2 and 2 in the existing wall panel P1 for the building, a foundation new-construction process in which an anew constructed foundation in which an anchor bolt is implanted is annexed outside an existing foundation supporting the existing wall panel and a fixing process in which the vertical frame materials on both sides of the opening section and the anchor bolt are connected by fixtures.