Cinnamon has been used for neuralgia on the knees and waist, and it is shown to have a wide antibacterial spectrum in both Gram-positive bacteria and Gram-negative bacteria. In this study, glucosyltransferase adhesive ability, acid-production suppression effect, and antibacterial activity were measured to identify the anti-caries effect of cinnamon extract. It was shown that cinnamon extract effectively suppressed acid production and bacterial adhesion for Streptococcus mutans and Streptococcus sanguinis . Additionally, the measurement result of the minimum inhibitory concentration of the cinnamon extract showed that the bacterial growth and development was inhibited at a 4 mg/ml concentration for anti-caries bacteria. In terms of the minimum bactericidal concentration, 99.99% bactericidal action was also confirmed at 4 mg/ml, and a high bactericidal action was shown with the smallest concentration for cariogenic bacteria. With regard to the adhesion-inhibition of glucosyltransferase, which is an oral pathogen for Streptococcus mutans that typically causes dental, caries among oral pathogens, the inhibitory effect appeared to be based on the concentration of the cinnamon extract, thereby showing that cinnamon extract has the ability to inhibit the fraction’s adhesion. Based on the results, it is concluded that cinnamon extract has the potential to be used as a natural antibacterial agent for oral pathogens, as it possesses acid-production suppression ability, the bactericidal action of the minimum bactericidal concentration, adhesion-inhibition ability, and anticaries effect.