An experimental study has been made on the extraction of chromium（VI） ion through a W/O/W liquid membrane which contains tridodecylamine as a carrier. Operating conditions for the stable W/O emulsion, determined from the measurements of the emulsion breakups, were that the concentration of surfactant, Span 80, is 3 wt percent and that the volume ratio of the inner aqueous phase and the oil phase is 1/2. The extractions were carried out under these stable conditions. More than 90 % of chromium(VI) ion with its initial concentration of 1,000 ppm can be extracted with two stages in 10 minutes when the concentration of carrier is 3 wt percent, when the concentration of NaOH in the inner aqueous phase is 0.1 N, and when the volume ratio of the emulsion and the waste water is 1/5.