A whitening agent containing, as the active ingredient, a whey protein hydrolyzate, which has the characteristics of showing the main peak at 200 Da to 3 kDa in the molecular weight distribution of 10 kDa or less, having an APL (average peptide chain length) of 2 to 8, having a free amino acid content of 20% or less and having an antigenicity 1/10,000 times or less as high as the antigenicity of β-lactoglobulin, exerting an excellent whitening effect on the skin and being efficacious in preventing and treating spots, freckles and so on； and whitening products such as a cosmetic, a food, a drink, a feed and a drug each containing the whitening agent as described above.
