Here we report a rare case of peritonitis caused by radiation enteritis. The 82-year-old woman who underwent surgery and radiotherapy for uterine cancer in her 30s. Emergency operation was performed for the perforation of the ileum. The small intestine showed changes of radiation enteritis extensively on macroscopy. The first surgery was performed to resect the perforated ileum and make intestinal anastomosis at the change of radiation enteritis. However, suture failure was occurred, reoperation was performed after conservative therapy. Reoperation was performed extensively resection of the intestinal tract and made anastomosis where was mild change of radiation enteritis. Pathological findings of the intestinal stump revealed that the arterial vessels of the submucosal layer were highly thicken and the lumen of artery was stenosis and occlusion with severe changes of radiation enteritis at the first operation. Blood flow disorders by irradiation were presumed to be the cause of suture failure. On the other hand, the intestinal stump did not indicate thickened of vascular wall and lumen stenosis of the vessels, only edematous changes in the submucosal layer were observed at the reoperation. It was important to determine the surgical procedure with the change of radiation enteritis for gastrointestinal operation with abdominal irradiation.