It has been believed that supplementation of human diets with soybean products markedly reduces human cancer mortality rates. Specifically the black colored soybean has been considered as having a medicinal effect since ancient times in Korea. Six genotypes of black colored soybean and a normal variety were investigated for their biological effect. While the isoflavone content of black colored soybean was higher than the normal soybean, saponin content of the seeds was not different among varieties. In the case of antioxidant activity, black colored soybean showed over 3 times increase in the active effect than the control variety. When feeding soybean extract, a general change of alcohol resolving effect, such as alcohol dehydrogenase activity, was observed in the blood and liver of rats.