Disclosed is a copper-zinc alloy electroplating bath, and a plating method using the same, capable of forming a uniform, brilliant plated layer of the intended composition and having a wide current density range, without the use of a cyanogen compound. The copper-zinc alloy electroplating bath contains a copper salt, a zinc salt, a pyrophosphoric acid alkali metal salt or a tartaric acid alkali metal salt, and nitrate ions. It is preferable that the concentration of the aforementioned nitrate ions be 0.001-0.050 mol / L. Furthermore, it is preferable that the pH of the aforementioned copper-zinc alloy electroplating bath be in the range of 8-14. Furthermore, in addition to the copper salt, zinc salt, pyrophosphoric acid alkali metal salt, and nitrate ions, it is preferable that an amino acid or at least one salt thereof be included, and histidine can be used favorably as the aforementioned amino acid.