We report herein the case of a 38-year-old man found to have a rectal arteriovenous malformation (AVM). The patient was admitted to our hospital for investigation of fresh anal bleeding and general malaise. Barium-enema examination showed a slightly elevated lesion in the rectum, and a selective superior rectal angiogram subsequently revealed an AVM in the peripheral region of the superior rectal artery, which was presumed to be the cause of the anal bleeding. Colonoscopic examination disclosed a submucosal tumor-like lesion in the left posterior wall of the rectum, 3cm above the anal verge. After marking the boundaries by clipping, transanal resection of the lesion was performed. Histological examination revealed an irregularly expanded arteriovenous aggregation in the submucosal layer. The patient had a favorable postoperative course, and no residual AVM was seen on a postoperative selective inferior mesenteric arteriogram. There have been no signs of recurrence in the 2 years since his operation.