A sealing device that is provided between a rotor extending along an axis as a center and a stator (5, 11) disposed on an outer peripheral side of the rotor, when the sealing device is mounted around the rotor, the sealing device comprising: a sealing body that is configured to seal a gap between the rotor and itself, when the sealing device is mounted in the stator; a fastening bolt that is configured to fix the sealing body to the stator, when the sealing device is mounted in the stator; and a bolt sealing part (, 25) that is disposed so as to cover a central axis (Oc) of the fastening bolt and seals a gap around the fastening bolt, wherein the sealing body includes a facing surface that is configured to oppose a fixing surface of the stator facing in an axial direction in which the axis extends when the sealing device is mounted in the stator, and a body through-hole that penetrates the sealing body so as to be opened on the facing surface, a head portion of the fastening bolt is inserted into the body through-hole and a tip portion of the fastening bolt is is configured to fix to a fixing hole formed on the fixing surface, when the sealing device is mounted in the stator, characterized in that the sealing device further comprises: a ring member that includes: a first ring-facing surface opposite to the facing surface, a second ring-facing surface opposite to the fixing surface of the stator, when the sealing device is mounted in the stator and a ring through-hole into which the fastening bolt is inserted and thereby penetrates toward the second ring-facing surface from the first ring-facing surface, wherein the bolt sealing part is provided between the facing surface and the first ring-facing surface and between the fixing surface and the second ring-facing surface, when the sealing device is mounted in the stator. a sealing body that is configured to seal a gap between the rotor and itself, when the sealing device is mounted in the stator; a fastening bolt that is configured to fix the sealing body to the stator, when the sealing device is mounted in the stator; and a bolt sealing part (, 25) that is disposed so as to cover a central axis (Oc) of the fastening bolt and seals a gap around the fastening bolt, wherein the sealing body includes a facing surface that is configured to oppose a fixing surface of the stator facing in an axial direction in which the axis extends when the sealing device is mounted in the stator, and a body through-hole that penetrates the sealing body so as to be opened on the facing surface, a head portion of the fastening bolt is inserted into the body through-hole and a tip portion of the fastening bolt is is configured to fix to a fixing hole formed on the fixing surface, when the sealing device is mounted in the stator, characterized in that the sealing device further comprises: a ring member that includes: a first ring-facing surface opposite to the facing surface, a second ring-facing surface opposite to the fixing surface of the stator, when the sealing device is mounted in the stator and a ring through-hole into which the fastening bolt is inserted and thereby penetrates toward the second ring-facing surface from the first ring-facing surface, wherein the bolt sealing part is provided between the facing surface and the first ring-facing surface and between the fixing surface and the second ring-facing surface, when the sealing device is mounted in the stator. a first ring-facing surface opposite to the facing surface, a second ring-facing surface opposite to the fixing surface of the stator, when the sealing device is mounted in the stator and a ring through-hole into which the fastening bolt is inserted and thereby penetrates toward the second ring-facing surface from the first ring-facing surface, wherein the bolt sealing part is provided between the facing surface and the first ring-facing surface and between the fixing surface and the second ring-facing surface, when the sealing device is mounted in the stator.