An in-mold decorating sheet is set in an injection mold and, after clamping the mold, molten molding resin is injected into the mold and allowed to cool and solidified, and part of the in-mold decorating sheet is integrally bonding to a surface of the molding resin, by which a molded resin product is obtained. After these processes, when the in-mold decorating sheet is peeled off from the surface of the molded resin product in compliance with conditions of ASTM D903, the in-mold decorating sheet has a peel strength of at least not less than 1 kgf/inch width or the in-mold decorating sheet breaks before reaching the peel strength. Therefore, an unnecessary portion of the in-mold decorating sheet is easy to trim from the surface of the molded resin product.