This investigation was performed to study the antioxidant activities and the antimicrobial effect of plum (Santarosa, Oishiwase) extracts. Plums were extracted by ultrasound-assisted method and boiling method. All extracts of plums showed concentration-dependent inhibitory effects on the DPPH free radical scavenging activity. In the superoxide anion radical scavenging method, all the plum extracts showed lower activity than BHT. But in case of sonicate extract of Oishwase exhibited the highest activity in plum extracts. The antimicrobial effect of plums used for human skin- or oral cavity-presented strains; Bacillus cereus (KCTC 1012) and Staphylococcus aureus (KCTC 1927). Addition of plum extracts was used by autoclaved and filtrated. Each extract solution was added into culture media with several concentration and then the bacteria cell growth was investigated for 72 hours. The effect of antimicrobial activities showed in a higher Staphylococcus aureus than Bacillus cereus. Results indicate that the autoclaved sample showed a higher antimicrobial activity than did the filtrated sample.