Provided is a method for producing cobalt sulfate, wherein impurities are effectively removed in a step for obtaining a cobalt sulfate solution having a high cobalt concentration by solvent extraction using an acidic organic extractant, thereby obtaining high-purity cobalt sulfate. When an acidic solution that contains calcium, magnesium and sodium as impurities is separated from a solution of cobalt chloride by solvent extraction, a diluent is added to an extractant to be used so that the resulting has a concentration of 10-30% by volume, preferably a concentration of 15-25% by volume, and the operational pH is maintained within the range of 4.0-5.0 and the organic phase/liquid phase volume ratio of the liquid is maintained within the range of 5.0-7.0 during a first step, the operational pH is maintained within the range of 4.0-4.5 and the organic phase/liquid phase volume ratio of the liquid is maintained within the range of 5.0-10.0 during a second step, and the operational pH is maintained within the range of 0.5-1.0 during a third step. Consequently, the concentration ratios of calcium, magnesium and sodium relative to the cobalt concentration in the obtained cobalt sulfate solution are respectively reduced to 0.0001 or less, 0.0001 or less and 0.00005 or less.