To efficiently remove lead ion to a low concn. when lead ion is removed from an aq. soln. containing lead ion produced in the production process of nickel by bringing the aq. soln. containing lead ion into contact with an org. solvent having a thiophosphinic acid structure to extract and remove the lead ion.

Lead ion can be efficiently removed by bringing a soln. containing lead ion into contact with an org. solvent phase having a thiophosphinic acid structure. In this process, the aq. soln. used is preferably a chloride soln. such as nickel chloride soln. The concn. of the extracting agent used to extract the lead ion is controlled to 1 to 50 v/v %, and the temp. of the aq. soln. and the extracting agent is controlled to 20 to 60°C. When the extracted lead is subjected to back extraction, the pH of the water phase is preferably controlled to ≥2. The thiophosphinic acid used is not limited, and an org. compd. having a structure expressed by the formula (wherein R is an alkyl group) is preferable.