Biological activity-promoting compositions containing soybean germ-origin isoflavone aglycone which promote human or mammalian health and exert effective effects of preventing or treating diseases when absorbed into the body by oral administration, instillation, etc., thereby contributing to the maintenance and promotion of human or mammalian health, prevention of diseases and so on. The biological activity-promoting compositions are characterized by comprising an isoflavone aglycone concentrate which is prepared by fermenting the soybean germ with koji mold to thereby decompose proteins, then hydrolyzing the same and further extracting and concentrating the resultant product with a solvent. The compositions are further characterized in that the content of daidzein amounts is at least 70% by weight based on the isoflavone aglycone in the concentrate.