Disclosed are a culture medium, an additive, and a method for efficiently inducing the differentiation of mammalian somatic stem cells into cells having the characteristics of adipocytes under conditions of serum-free or low-serum culture medium. The culture medium for inducing the differentiation of mammalian somatic stem cells into adipocytes comprises a basal medium for culturing mammalian cells, an agent for inducing the differentiation of mammalian somatic stem cells into adipocytes, biotin, a ligand for endothelial cell differentiation gene (Edg) family receptors, vitamin C, and HEPES, which culture medium is serum-free or contains a low concentration of serum.