We performed thoracoscopic surgery for a mediastinal bronchogenic cyst with complaining of back pain. The patient, a 38-year-old male, was admitted with an abnormal shadow on chest X-ray. Chest CT showed a localized tumor on the mediastine. MRI showed a cyst. Under thoracoscopy the tumor was based on parietal pleura and movable in chest cavity. We concluded that back pain was caused by a stimulus of a nerve in parietal pleura. Pathological diagnosis was a bronchogenic cyst.