A sealing system is equipped with a dry gas seal having a rotating ring positioned between a casing and a rotor shaft and around the circumference of the rotor shaft, and stationary rings provided on the casing with elastic members interposed therebetween and so as to be capable of contacting the orthogonal edge surfaces of the rotating ring that are substantially orthogonal to the rotor shaft; a sealing gas channel having one end connected to a discharge channel, the other end connected so as to connect to a space between the casing and the outer perimeter surface of the rotating ring in the dry gas seal, and having a sealing gas regulating valve provided therein; and a drain gas channel having one end connected so as to connect to the space via a through hole formed in the casing below the rotating ring, and the other end connected to an intake channel.