We conducted to evaluate the antimicrobial effect of the Nelumbo nucifera leaf extract on oral diseaseinducing bacteria. The strains used in this experiment were investigated for nine types of Streptococcus strains. The antimicrobial activity of Nelumbo nucifera leaf extract was measured by the paper disk agar method and minimal inhibitory concentration (MIC). As a result, the methanol extract of Nelumbo nucifera leaf showed the strongest antimicrobial activity against S. anginosus and F. nucleatum, and the weakest activity against S. oralis and S. gordonii. Methanol extract was absorbed into the paper disk (Φ 8 mm) and the diameter (mm) of the clear zone was measured. The result of the MIC was nearly consistent with the result of the antimicrobial activity that was measured via the paper disk method in that the antimicrobial activity against S. anginosus was the strongest, while the antimicrobial activity against S. gordonii was the weakest. Therefore, Nelumbo nucifera leaf extract can be used effectively in the prevention of oral diseases.