Objectives : Prunus mume has been used for the folk medicine from old times. The purpose of the study was to investigate the antimicrobial activity of prunus mume extract to various oral microbes. Methods : This study was carried out to examine the antimicrobial effect of Prunus mume extract against oral microbes. Data were collected using a Dentocult SM Strip mutans and Dentocult LB Strip mutans from April 5 to May 4, 2013. A total of 36 experimental and 32 control group were selected for this study. Results : The MIC of Prunus mume extract was tested for 0.39% in S. mutans, S. salivarius and S. auerus, 0.78% in S. mitis, S. equi and E. coli. In vivo, experimental group showed significantly the lower Streptococcus mutans levels by the use of the gum contained Prunus mume extract from 15 days compared with control group(p=0.012). The reduction was more significant in Lactobacilli level of the experimental group than the control group(p=0.022). Conclusions : These findings suggest that the oral products containing Prunus mume extracts is effective in preventing oral diseases.