The lactulose contents in market milks were analyzed by gas chromatographic method. The method is evaluated for accurac and reproducibility using phenyl-$eta$-D-glucoside as an internal standard. The response factor(RF) of lactulose of standard mixture was 1.15 the recoveries were 97.4-101.3% and the reproducibility was determined on the coefficeitns of variation 24.8% for pasteurized milk and 4.6-4.9% for UHT milk The lactulose contents of 16 brands of the market milks determined were 5.3-59.7mg/100ml in UHT milk and 1.3-1.8mg/100ml in pasteurized milk.