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In order to construct a practical extraction recovery process of organic, phosphorous and hypophosphorous acids from wastewater of electroless nickel-plating with tri-n-octylamine in toluene, a closed circulation type continuous extraction equipments with the extraction and the back-extraction steps were developed. Two equipments, which were a laboratory scale having 30 ml reactor and a pilot plant scale having 450 ml reactor, were constructed with reactors having multiple vibration disks in a cylindrical tube for extraction and back-extraction, the settler for oil/water separation and the metering pump for transportation of the organic and the aqueous phase. The effect of pH and its control in the aqueous phase on these acids extraction were investigated using the laboratory scale equipment. The experiments using the pilot scale equipment, whose experimental condition was selected based on the acids extraction behavior in the laboratory scale equipment, was done to determine the practical conditions. In the treatment of a spent electroless plating bath using the pilot scale equipment, the treatable volume of the wastewater was 210 L/24 hr, and the recovered mass for hypophosphorous acid and phosphorous acid were 3.4 kg and 1.1 kg for 24 hr.