A 73-year-old man visited our hospital with the chief complaints of anorexia and weight loss. Computed tomography showed a 5 cm tumor(diameter)in the sigmoid mesocolon. We performed laparoscopic Hartmann operation; however, because of sacral invasion of tumor, curative surgery was difficult. Therefore, the tumor was excised together with the sigmoid colon. Histopathological examination of the tumor confirmed the diagnosis of epithelioid sarcoma. Postoperatively, the patient received heavy-particle radiotherapy at another facility as treatment for the residual tumor. The size of the residual tumor decreased 6 months after the surgery. Up until 1 year after surgery, the patient's condition has remained stable without any disease progression. Epithelioid sarcoma is a rare soft-tissue tumor and often leads to a poor prognosis. We present a case of epithelioid sarcoma occurring in the sigmoid mesocolon.