The invention addresses the problem of providing a skin-beautifying agent with beautifying effects such as skin moisturizing, skin beautification, prevention of rough skin, wrinkle prevention, prevention of reduced elasticity, etc., and a skin-beautifying product such as a cosmetic, food or drink, feed, medicine, etc. that contains said skin-beautifying agent. The skin-beautifying agent is characterized in containing a hydrolyzate of whey protein as an active ingredient. Using a whey protein hydrolyzate having the characteristics of a molecular weight distribution of 10 kDa or less, a main peak of 200 Da-3 kDa, APL (average peptide length) of 2-8, free amino acid content of 20% or less, and a β-lactoglobulin antigenicity of 1/10,000 or less, in particular, provides a skin-beautifying agent of low allergenicity and low bitterness.