Congenital duodenal obstruction is a one of the emergent surgical conditions in neonates. Almost of them were diagnosed with double-bubble sign in prenatal ultrasonography. However, partial obstruction caused from duodenal web could be overlooked. We reported a duodenal web in early childhood. A three-year-old girl visited at our pediatric clinic for constipation. She had been showed non-bilious vomiting after weaning meal since 6 months old of her age, but her weight was relevant for 50-75 percentile of growth curve. Barium enema was initially checked, but any abnormal finding was not found. We noticed the severely distended stomach and 1st portion of duodenum. Upper gastrointestinal series revealed partial obstruction in 2nd portion of duodenum. After laparotomy, we found the transitional zone of duodenum and identified a duodenal web via duodenotomy. We performed duodeno-duodenostomy without any injury of ampulla of Vater. She was recovered uneventfully. During 6 months after operation, she does well without any gastrointestinal symptoms or signs, such as vomiting or constipation.