Electrolytic copper plating solution and method of electrolytic copper plating

An electrolytic copper plating solution is provided which has an excellent via filling ability without using formaldehyde, which is harmful to the environment. An electrolytic copper plating solution which contains compounds which have an -X-S-Y- structure wherein X and Y are individually atoms selected from a group comprising hydrogen, carbon, sulfur, nitrogen, and oxygen atoms and X and Y can be the same only when they are carbon atoms and specific nitrogen-containing compounds. Good filled vias can be made without causing a worsening of the exterior appearance of the plating by using this electrolytic copper plating solution.