The research aimed to investigate the corrosion behavior of Cu–Sn–Zn–S alloy（as one of lead–free Cu alloys）in CuCl₂ aqueous solutions. JIS CAC411（Cu–Sn–Zn–S alloy）, Cu and Sn were used as specimens. Test solutions were CuCl₂ ＋ NaCl solutions whose Cu^2＋ and Cl⁻ concentrations were controlled. A polarization curve of each specimen in each solution was measured. The results were described as follows：Increase in Cu^2＋ concentration accelerated cathodic reaction and made corrosion potential of Cu and CAC411 specimens higher, however hardly changed shapes of the anodic polarization curves. On the other hands, increase in Cl⁻ concentration accelerated anodic reaction and decrease corrosion potential of Cu and CAC411 specimens. 1.0 mass％ CuCl₂ solution which generally employed in the jet–in–slit test facilitated to form corrosion product layer consisting of CuCl. Sn was concentrated in the corrosion product layer formed on CAC411 specimen. The particles of the corrosion product formed on CAC411 was finer and the corrosion product layer was denser than that on Cu.