The meconium peritonitis is rare, and there had been-reported by Simpson; (1838), and other authors. We have found meconium peritonitis arising in twin who developed generalized in one and localized in another one. The diagnosis was confirmed by radiological evidence, operation findings and autopsy findings. The cause of meconium peritonitis in first twin baby has revealed as defect of serosal layer of intestinal wall. They died probably from intra-alveolar hemorrhage. This is the first reported case of meconium peritonitis in twin in Korea.