A steam turbine according to an embodiment of the present invention includes: a rotor configured to rotate about an axis; a casing which houses the rotor; 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. 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. 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.