Synovial sarcoma is an uncommon, malignant tumor which originates from the synovial lining of the joints, bursae and tendon sheaths. But it rarely occurs from bones. We have experienced a synovial sarcoma of the left ulna. Microscopically cleft spaces lined by epithelioid cells and bundle formation by spindle spaped cells were seen. Above elbow amputation of the left arm was done.