After sawing in the intraoral vertical ramus osteotomy, in the case of an incomplete amputation, the proximal segment is split using the osteotome. Unfortunately, in this case, the proximal segment was accidentally fractured. The operation was completed without performing any other fixation. Postoperatively intermaxillary fixation was performed and kept for a week, followed by physical therapy, which was initiated immediately after. The patient was closely observed for 6 months. No abnormal findings were detected clinically, and the union of bone was verified.