Brunner's gland adenoma is a rare benign small bowel neoplasm and it represents 10% of small bowel benign tumor. Most of adenoma manifest as polypoidal, multiple and size does not exceed 1 cm and mostly asymptomatic, but the lesion larger than 1 ㎝ is solitary and can cause bleeding, obstruction, intussusception and there are some reports of showing malignant transformation. Until the present, there are two cases of over 8㎝ huge Brunner's gland adenoma in Korea and each of their chief complaint was abdominal discomfort and melena, but there is no case report of over 8 ㎝ Brunner's gland adenoma accompanied with acute bleeding as seen in this case. We diagnosed an 8 ㎝ sized, huge duodenal Brunner's gland adenoma which accompanied with acute bleeding and treated it by endoscopic resection using an IT-knife, successfully.