The diverticulm of the stomach is an unusual anomaly of the upper gastrointestinal tract. The first case of diverticulum of the stomach was reported by Baillie in 1793, since that time 412 cases were reported by 1951. The gastric diverticula are usually symptomless and discovered incidentally during X-ray and endoscopic examination. The most common location of gastric diverticular was juxtacardiac region and next was pylorus. In our hospital, one case of gastric diverticulum was found. That 16 years old male patient had been suffered from intermittent upper abdominal pain for several years. Chest P-A and plain abdomen were checked before admission and air-fluidlevel was seen on left upper quadrant of abdomen. After admission, upper gastrointestinal series was peformed andwe found giant gastric diverticulum on upper portion of greater curvature with duodenal ulcer. The diagnosis of true diverticulum of stomach was confirmed surgically and pathologically.