Most of the leachate were found to contain a relatively large amount of organics (COD>1000 mg/ℓ), which would exert additional demand for oxidizing agents like as chlorine. The foam of the cyanide in the leachate was found to be iron-cyanide complexes that resist oxidation by a conventional treatment method. In this study, among several chemical oxidation methods. UV irradiation with or wighout ozone was investigated as a treatment option. The followings are the primary findings: UV irradiation alone was effective for removing the iron-cyanide complex in the leachate. Ozone alone was not effective for removing the iron-cyanide complex and UV irradiation alone and UV irradiation with ozone resulted in the same removal for total cyanide, but the UV irradiation left some free cyanide whereas the UV irradiation with ozone did not.