We report a case of an unruptured aneurysm of the right gastroepiploic artery in a 56-year-old woman, who complained of constant abdominal pain. Abdominal CT showed an intramesenteric hematoma in the ventral side of the left kidney and an aneurysm of the right gastroepiploic artery. Since her abdominal pain had not improved, the hematoma was removed, and the unruptured aneurysm of the right gastroepiploic artery was resected laparoscopically. On pathology, the aneurysm was found to be caused by segmental arterial mediolysis. An aneurysm of the gastroepiploic artery is rare ; many of the cases are diagnosed after they rupture. However, recently the number of cases found incidentally on ultrasonography or abdominal CT is increasing. There are no recognized indications related to surgery for an aneurysm of the gastroepiploic artery. However, resection of the aneurysm laparoscopically is minimally invasive, safe, and therefore can be recommended.