Several natural products were tested to control the differentiation of cultured human mesenchymal stem cell into adipocyte. The extent of the inhibitory effect on the conversion of adipose was measured using Oil red O staining, which stains accumulated lipid droplets in the cytoplasm of adipocyte. Of the various natural product extracts, the adipocyte differentiation was inhibited by an extract from Folium mori in the concentration range 1${ imes}$10$^$-4/∼5${ imes}$l0$^$-2/ g/mL. These results suggest that Folium mori has an inhibitory activity toward the adipose conversion, which is a major cause of obesity.