A 49-year-old man was admitted for the further examination of the abnormal shadow of the left posterior mediastinum, which was incidentally detected on routine chest X-ray. He has no complaints, and no abnormalities on neurological examination. Thoracic spine X-ray showed the destruction of the T12 vertebral body and the dilatation of the left intervertebral foramen between T12 and L1. Myelography showed no abnormalities, but contrast-enhanced CT scanned just after myelography revealed the extradural dumbbell-formed tumor. One stage removal of the tumor was safely performed through left posterolateral thoracotomy and transthoracic partial laminectomy. Postoperative course was uneventful. The tumor was histologically schwannoma, originated from the left thoracic sympathetic trunk. We think that this procedure is available for the operation of a kind of dumbbell tumor of the posterior mediastinum.