For the electrolysis of cobalt the separation of nickel from cobalt pregnant solution by precipitating nickel as nickel Nioxime was studied. The effect of the pH and temperature for the precipitation of nickel was determined. The cobalt electrolyte in the order of the magnitude of the ratio of Ni/Co=n×10^<-4> for electrolysis was obtained by the addition of Nioxime at the pH of 3 to 4 and the temperature of 20° to 80℃.