The purpose of this investigation is to observe tha variation of vitamin $B_{12}$, nicotinic acid and folic acid contents in relation to the growing years of Panax Ginseng roots. The contents of the vitamins were estiamted microbiologically with Lactobacillus leichmannii, Lactobacillus arabinosus and Streptococcus faecalis, respectively. It is found that the content of vitamin $B_{12}$ in Panax Ginseng roots somewhat increases according to their growing years except 3-year-old roots. It is probable that the lower content in these roots should be due to the cultivating soil. The content of nicotinic acid in all the roots is not significantly different. The result of paper chromatography using the concentrated extract of the roots suggests that there exists some other substance besides nicotinic acid and nicotinamide, of which Rf value is 0.5 in comparison with the Rf 0.75 of nicotinic acid and nicotinamide. It is thought that this substance stimulate the growth of L. arabinosus. The content of folic acid is significantly different. The content level is the highest in the 4-year-old roots and the lowest in the 6-year-old roots.