We report a case of ganglioneuroblastoma occurring in the superior mediastinum in adult. A 63-year-old man was admitted to our hospital for detailed investigation of an abnormal shadow on his chest radiograph. Chest radiography and CT imaging showed a left superior mediastinal tumor. Histopathologically, the tumor was identified as a ganglioneuroblastoma. Although ganglioneuroblastomas occur predominantly in children, 3 cases have been reported in adults in Japan. Incidentally, this is the first reported case of ganglioneuroblastoma occurring in the superior mediastinum in Japan.