. "an alkyl group, A is an epoxy compound residue, X.sub.1.sup.- is Cl.sup.-, Br.sup.- or CH.sub.3SO.sub.4.sup.-, and n is an integer of 1 or greater.)[2] The copper electrolytic solution according to the above [1], in which the epoxy compound residue A of the quaternary amine compound with a specific skeleton has a linear ether linkage.[3] The copper electrolytic solution according to the above [1]" . . .