A rotating machine such as a steam turbine, a gas turbine, or the like, comprising: a rotor having a rotor main body that rotates about an axis thereof, and a rotor blade disposed to extend from the rotor main body outward in a radial direction; a casing disposed to surround the rotor from an outer circumferential side and having a cavity that a tip of the rotor blade enters; a plurality of sealing fins (17A, 17B, 17C) extending from an inner circumferential surface of the cavity of the casing toward the tip of the rotor blade and configured to seal a space between the casing and the rotor blade; and swirl breakers disposed between the plurality of sealing fins (17A, 17B, 17C), extending from the inner circumferential surface of the cavity of the casing inward in the radial direction, and having swirl flow collision surfaces with which a swirl flow collides and swirl flow transmission parts formed at at least parts of the swirl flow collision surfaces and through which the swirl flow passes in a circumferential direction, characterized in that the swirl breakers are formed of a plate-shaped body and in between the sealing fin at an upstream side (17A, 17B) and the sealing fin at a downstream side (17B, 17C), and the swirl flow collision surfaces are formed to have different angles with respect to the axial direction at a proximal end side and a tip side, and the swirl flow transmission parts (n) are gaps formed between the swirl flow collision surfaces and at least one of the sealing fins (17A, 17B, 17C) of one side in an axial direction and another of the sealing fins (17A, 17B, 17C) of the other side in the axial direction. a rotor having a rotor main body that rotates about an axis thereof, and a rotor blade disposed to extend from the rotor main body outward in a radial direction; a casing disposed to surround the rotor from an outer circumferential side and having a cavity that a tip of the rotor blade enters; a plurality of sealing fins (17A, 17B, 17C) extending from an inner circumferential surface of the cavity of the casing toward the tip of the rotor blade and configured to seal a space between the casing and the rotor blade; and swirl breakers disposed between the plurality of sealing fins (17A, 17B, 17C), extending from the inner circumferential surface of the cavity of the casing inward in the radial direction, and having swirl flow collision surfaces with which a swirl flow collides and swirl flow transmission parts formed at at least parts of the swirl flow collision surfaces and through which the swirl flow passes in a circumferential direction, characterized in that the swirl breakers are formed of a plate-shaped body and in between the sealing fin at an upstream side (17A, 17B) and the sealing fin at a downstream side (17B, 17C), and the swirl flow collision surfaces are formed to have different angles with respect to the axial direction at a proximal end side and a tip side, and the swirl flow transmission parts (n) are gaps formed between the swirl flow collision surfaces and at least one of the sealing fins (17A, 17B, 17C) of one side in an axial direction and another of the sealing fins (17A, 17B, 17C) of the other side in the axial direction.