To provide a copper-zinc alloy electroplating bath in which a cyan compound is not contained and from which a plated film having excellent corrosion resistance is formed, and to provide a wire for a steel cord.

The copper-zinc alloy electroplating bath contains copper salt, zinc salt, alkali metal pyrophosphate and at least one selected from amino acids and the salts thereof and has 5% volumetric molar concentration ratio (A/M) (wherein A is the volumetric molar concentration of the amino acid or the salt thereof; and M is the total volumetric molar concentration of the copper ions and zinc ions contained in the copper-zinc alloy electroplating bath).