The resin composition for a platable substrate of the present invention comprises 100 parts by weight of a resin composition (C) comprising 10 to 60% by weight of a graft copolymer (A) prepared by graft polymerization of a rubbery polymer (A1) and a monomer component (A2) containing an aromatic alkenyl compound monomer unit (a) and a vinyl cyanide compound monomer unit (b) and 40 to 90% by weight of the other polymer (B) (provided that the total amount of the components (A) and (B) is 100% by weight), and 5 to 40 parts by weight of a phosphate ester flame retardant (D) having a molecular weight of more than 326 or 2 to 40 parts by weight of a red phosphorus flame retardant (D'). The resin composition for a platable substrate of the present invention is excellent in production stability such as moldability, dimensional stability, mechanical strength and plating properties, and is also environmentally friendly. Excellent plated parts having good thermal conductivity can be provided by forming a metal plating layer on a resin molded article obtained by molding the resin composition for a platable substrate using a plating treatment. The resulting plated parts are suitable for use as housings for laptop PC and portable devices.