Objectives: The purpose of the present study was to investigate the effect of bamboo charcoal on Streptococcus mutans which is one of the most important causative agents of dental caries. Methods: S. mutans was incubated with or without bamboo charcoal and then changes were observed in its cell viability and antibacterial effect. Oral epithelial cells viabillity(human gingival fibroblast, HGF) was performed using MTT assay. Antibacterial effect was analyzed using a dilution plating method and agar diffusion method. Results: Oral epithelial cells, human gingival fibroblast (HGF) showed a tendency to increase in bamboo charcoal treatment solution concentrations(0.5 , 1, 2 , 3 , 5, 10%). The bamboo charcoal had an antibacterial effect on S. mutans. Antibacterial effect of bamboo charcoal for the bacterium was 58%. Charcoal concentration of 2% and 5% in the inhibition zone showed a minimal growth, but the concentration of 10% bamboo charcoal in inhibition zone revealed a conspicuous antibacterial activity. Conclusions: Overall results suggested that the bamboo charcoal proved to be bactericidal effect on S. mutans.