Steam turbine

A steam turbine, comprising:

• a rotor configured to rotate about an axis;
• a casing which houses the rotor rotatably;
• and
• a first stage including a first-stage stationary vane fixed to an inner wall portion of the casing and a first-stage rotor blade fixed to the rotor at downstream of the first-stage stationary vane,
• wherein the rotor includes a first cavity having a concave shape and being formed on a portion facing the first-stage stationary vane, the first cavity being in communication with an inner space defined between the inner wall portion and the rotor at upstream of the first-stage stationary vane,
• wherein the first-stage stationary vane includes a first-stage through hole which is in communication with the first cavity and which is formed through the first-stage stationary vane in a radial direction, and
• wherein the steam turbine is configured such that steam introduced from the first cavity via an inlet opening of the first-stage through hole flows through the first-stage through hole.