In order to electroplate the Ni-Zn alloy with high corrosion resistance onto the steel sheet, the behavior of electrodeposition of Ni-Zn alloy at high current densities has been studied. Because of raising the pH in the vicinity of the cathode in plating, the layer of zinc hydroxide is formed. Electrodeposition of Ni-Zn occurs through this layer. So electrodeposition of Ni-Zn alloy is effected strongly on the pH in the vicinity of cathode surface. In order to obtain the γ-phase Ni-Zn alloy film with high corrosion resistance, it is effective to maintain the condition in the vicinity of the cathode surface. Therefore, it is important not only to maintain the operating condition, such as bath composition, current density and pH, but also to give the steel strip a certain of flow rate, for obtaining a uniform alloy coated steel sheet.