The present invention provides a technology for, in copper electrolytic plating containing silver ions as an alloy component, obtaining a copper electrolytic plating film in which co-deposition of sulfur can be significantly suppressed and which is excellent in physical properties such as strength and hardness even after a high-temperature heat treatment at about 200° C. or higher. The present invention is a copper electrolytic plating bath comprising copper ions, an acid, chloride ions, and a complexing agent, wherein the copper electrolytic plating bath further comprises silver ions as an alloy component, and wherein methionine or a derivative thereof is contained as the complexing agent.