A 55-year-old man seen at the hospital because of an abdominal tumor was found to have a solid and cystic tumor occupying the whole abdomen by abdominal CT scan. In abdominal magnetic resonance imaging scan, T1 emphasis image showed the low signal intensity, and T2 emphasis image showed the high signal intensity. Abdominal angiographic findings indicated that the left and right gastroepiploic arteries fed the tumor. Operation was performed with a diagnosis of primary malignant tomor arisen in the greater omentum. The excised specimen consisted of two tumors, a tumor 23×21×16 cm and the other 15×9×6 cm in dimention, and was 2730g in gross weight. Histopathologically, the tumor consisted of oval-shaped cells or polygonal cells and immunohistochemical stainings showed negative for c-kit and CD34, while positive for α smooth muscle actin. The histopathological diagnosis was epithelioid leiomyosarcoma. Furthermore, the tumor presented positive response in CA125 staining and was cossidered to be a very rare CA125-producing tumor in the male. No signs of recurrence have been found as of 1.5years after the operation.