Lubricant oil (45) serving as second lubricant oil is supplied into an outer intermediate shaft (11c) by a lubricant oil supply unit (50) and accumulated therein, and thereby the lubricant oil (45) is supplied to a contra-rotating front seal unit (37). Thus, by bringing the front side of the contra-rotating front seal unit (37) (seal ring (37b)) into a wet state by the lubricant oil (45), it is possible to reduce heat generation and it is possible to extend the life of the contra-rotating front seal unit (37).