This study was to investigate the intake of human milk, sodium and potassium of breast-fed infants at 7, 15, 30, 60 and 90 days postpartum. Milk samples were obtained from 20 healthy lactating women living in In-Cheon area. Milk intakes of 20 breastfed infants were determined by the test-weighing method and soldium and potassium contents of human milk were analyzed by Atomic Absorptin Spectrophotometer after Wet-Digestion. Infant milk intakes per day tended to increase during lactation. The mean($pm$SD) intakes at 7, 15, 30, 60 and 90 day were 460(164), 547(202), 626(199), 718(139) and 688(162)g/day, respectively. The sodium contents decreased significantly from 9.7(1.1)mEq/kg at 7 day to 6.3(1.8)mEq/kg at 90 day(p<0.05). The sodium intakes of infants were 100.8(39.6), 103.3(46.7), 107.2(47.9), 115.5(41.5) and 105.2(41.2)mg/day, respectively and average intake was 107.2(43.9)mg/day. The potassium contents were ranged from 10.5(1.3) to 13.3(2.3) mEq/kg and the potassium intakes of infants were 241.8(11.2), 267.8(98.8), 314.1(98.6), 318.0(66.1) and 276.1(62.6)mg/day, respectively and average intake was 288.3(91.8)mg/day. The mean sodium and potassium intakes of infants between boys and girls were not significantly different at 5% level.