Steam turbine

A steam turbine comprising:

• a rotary shaft configured to rotate about an axis;
• a rotor blade including a rotor blade body extending radially outward from the rotary shaft, and a shroud on an end outside in a radial direction;
• a casing enclosing the rotor blade from outside in the radial direction and including a cavity accommodating the shroud on an inner circumference of the casing;
• a plurality of seal fins protruding radially inward from an opposing surface that faces the shroud in the cavity such that a clearance is between an outer circumferential surface of the shroud and the plurality of plurality of seal fins;
• a plurality of swirl breaks upstream of the plurality of seal fins located furthest upstream in a direction of the axis in the cavity, the plurality of swirl breaks being arranged at intervals in a circumferential direction;
• and
• a protrusion on an edge of each of the plurality of swirl breaks, the protrusion protruding outward from each of the plurality of swirl breaks and having a triangular shape.