Abstract: A device for sealing the shaft of a turbo machine in which there are disposed a shaft sealing side plate attached to a casing, an atmospheric side floating ring and an in-machine side floating ring arranged in a seal case and associated with the shaft with the interposition of a small space, the atmospheric side floating ring having an atmospheric side end surface in contact with the shaft sealing side plate, the in-machine side floating ring having an in-machine side end surface in contact with the seal case; the device being characterized in that a flexible ring which is deformable in compliance with the deformation of the atmospheric side floating ring during driving is interposed between the atmospheric side floating ring and the shaft sealing side plate, whereby an excessive load is not applied between each white metal of both the floating rings and a seal sleeve, hardening and scalling loss of the white metal are prevented, and the reliability of sealing in the turbo machine is improved.