In conclusion, we evaluated the antimicrobial activities of aqueous extracts of herbal medicines against oral bacteria. Of the tested herbal medicines, Sappan Lignum and Psoraleae Semen showed the strongest antimicrobial activity against all of the bacteria tested; notably, this is the first report of the inhibitory effect of Sappan Lignum on oral bacteria. Therefore, these results suggest that herbal medicines with proven antimicrobial effects, such as Sappan Lignum and Psoraleae Semen, may be useful for the treatment of dental diseases.