585092 Provided is a milk protein fraction derived from milk, wherein the milk protein fraction contains proteins having a molecular weight of 80,000 to 85,000 daltons determined by sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), contains 16 to 18wt% of basic amino acids in the constituent amino acid composition, has a basic amino acid/acidic amino acid ratio of 0.65 to 0.85, and has an osteoclastogenesis inhibitory effect.