Active antibacterial compound against periodontitis-causing bacterium Porphyromonas gingivalis was isolated from Kaempferia pandurata and identified as panduratin A. Minimum inhibitory concentration (MIC) value of panduratin A was $4;{mu}g/mL$, much lower than those of other natural antibacterial agents. Panduratin A also showed antibacterial activity against Prevotella intermedia ($2;{mu}g/mL$), P. loescheii ($4;{mu}g/mL$), and cariogenic Streptococcus mutans ($4;{mu}g/mL$). Damage on cell wall and perturbation of cytoplasmic membrane of panduratin A-treated P. gingivalis were visualized through transmission electron microscopy. These results suggest panduratin A, exhibiting strong and preferential antiperiodontal and anticariogenic activities, may be utilized in functional foods for prevention of oral diseases.