We report a case of necrotic Meckel's diverticulum due to torsion at its neck, resulting in ileus. A 6-year-old boy was admitted with complaints of nausea and abdominal pain. Emergency laparotomy was performed under the suspicion of torsion of small intestine. A huge diverticulum, 90×60mm in size, was found on the ileum about 60cm proximal to Bauhin's valve. It was twisted about 360° clockwise at its neck and was necrotized. Wedge resection of the ileum with the Meckel's diverticulum was performed. Torsion is a rare complication of Meckel's diverticulum, and we found reports of only 17 other cases in Japan. Those diverticula were also large, greater than 6cm in length, and had narrow necks. In our case, we thought that the ileus was the result of torsion of Meckel's diverticulum, associated with peritoneal inflammation, and oppression by this huge diverticulum.