PURPOSE: To reduce shaft vibration by providing a resistance plate, having radial grooves formed to prevent the turning of an inflow fluid, on the upstream side of a labyrinth seal provided between a shaft and a casing.

CONSTITUTION: Labyrinth seal 14 as a sealing device is provided at a gap 13 between a shaft 11 and a casing 12, and a recessed part 15 coaxial with the shaft 11 is formed at a casing 12, on the fluid flow upstream side of the labyrinth seal 14. An annular resistance plate 16 is fitted at this recessed part 15 in such a way as to close the gap 13, and this resistance plate 16 is formed in the internal tooth gear state and provided with plural radial grooves 18. An operating fluid that is going to flow along the shaft 11 is stopped in its turning by these radial grooves 18, and that its flow speed is lowered before flowing into the labyrinth seal 14. The inner pressure change of the labyrinth seal 14 is not therefore generated easily, and thus shaft vibration is reduced.