In this study, to investigate the anticariogenic effect of red ginseng, the antibacterial effect, cell adherence and biofilm formation inhibitory effect of n-hexane extract of red ginseng marc (HERGM) against Streptococcus mutans, the causative bacteria of caries, were measured. The growth of S. mutans was inhibited in proportion to the concentration of HERGM, and was hardly observed at a concentration above 125 μg/mL (MIC =125 μg/mL). It was found that HERGM acts on the cell membrane and the nucleic acid component of the cell was leaked. In addition, HERGM inhibited the adherence and biofilm formation of S. mutans by more than 90% at a concentration of 125 μg/mL. GTase activity was completely inhibited at a concentration of 50 μg/mL of HERGM. In conclusion, it was found that HERGM commonly inhibited the growth and biofilm formation of S. mutans.Keywords Biofilm formation inhibition · Growth inhibition · n-hexane extract of red ginseng marc · Streptococcus mutans 서 론