This study was conducted to produce vinegar using maesil. Acetic acid bacteria was 20 strains isolated from several conventional vinegars. Among the isolates, a strain showed highest acetic acid productivity was selected and identified as Acetobacter sp. SK-7. The optimum medium of acetic acid production by Acetobacter sp. SK-7 was 30% of maesil juice, 4% of ethanol, and 2% of starting acidity and 0.2% of glucose. Optomum condition for the high yield of acetic acid was in the shaking culture at 30℃. The acidity of culture medium was reached to 7.1% after 12 days fermentation. Organic acid was identify 6 kinds containing acetic acid. The total content was 7,068.7 mg% after 12 days and malic acid slowly decreased and acetaic and citirc acid gradationally increased according to fermentation