Localized corrosion resistance of Co-Cr alloy in NaCl solution was investigated by using polarization curve measurements. Type 316 stainless steel and Cr were used as comparison materials. According to the polarization curves obtained in this study, the Co-Cr alloy maintained a passive state over a wide potential region. However, the current increment with the localized corrosion was appeared in polarization curves of the type 316 stainless steels. The Co-Cr alloy had high localized corrosion resistance compared to the type 316 stainless steel in NaCl solution. Co-Cr alloy was confirmed to maintain passive state in the potential region, same as that observed for Cr. In addition, the passive current density of the Co-Cr alloy and Cr showed nearly identical values. When used in the environment containing chloride ions, the Co-Cr alloy maintained high localized corrosion resistance with the existence of the chromium oxide film. Because of their excellent corrosion performance, Co-Cr alloys are expected to be safely used as the biomaterials in a long life time.