When an annular portion of a thrust collar rotates together with a rotating shaft member, centrifugal force and shear force, or differential pressure caused by difference in flow rate are generated in lubricating oil in a circulation oil chamber. With this, the lubricating oil in the circulation oil chamber is guided from the inner peripheral side to the outer peripheral side of the annular portion, through a circulation hole penetrating the annular portion. The flow of lubricating oil guided by the circulation hole forms a flow of lubricating oil from a lower oil chamber to an upper oil chamber through the circulation oil chamber. As a result, the lubricating oil stored in the lower oil chamber is circulated to the upper oil chamber through the circulation oil chamber, by rotation of the thrust collar.