PURPOSE: An auxiliary for metal plating resulting from emulsion polymerization of acrylonitrile and vinyl esters in the presence of a diene rubber is mixed with a thermoplastic resin to produce title composition capable of obtaining metal plating films with high adhesion.

CONSTITUTION: To (A) 100 parts by wt of a thermoplastic resin are admixed (A) 5W25, preferably 8W20 parts of an auxiliary for metal plating which is prepared by emulsion polymerization of 10W200, preferably 20W150 parts of monomer mixture consisting of (b2) 20W90 wt% of acrylonitrile and (b3) 80W10 wt% of at least one monomer selected from the group consisting of vinyl esters such as vinyl acetate, unsaturated carboxylic acid such as acrylic acid, unsaturated carboxylic esters, amides and unsaturated carboxylate metal salts in the presence of (b1) 100 parts of a diene rubber with a diene (butadiene or isoprene) monomer content of 50W100 wt%.