PURPOSE: To activate the surface of a hydrophobic, inert high polymer substance in such a way that uniform and stabilized treatment effects are obtained, by treating the surface of the high polymer substance with a detergent composition consisting of a solution of an organic solvent containing a surface active agent and a metallic complex compound and wiping.

CONSTITUTION: The surface of a hydrophobic, inert high polymer substance (e.g. polyolefin, etc.) is treated with a detergent composition consisting of (A) a surface active agent and (B) a solution of an organic substance (e.g. polyolefin, etc.) containing a metallic complex compound and wiped to modify the surface of the substance. Polyoxyethylene dodecyl phenyl ether, aliphatic diethanolamide, etc., are preferable as the component A, a metallic complex compound of phosphoric ester is preferable as the component B and further a hydrocarbon or halogenated hydrocarbon solvent is preferable as the organic solvent.