This steam turbine is provided with: a steam turbine rotor which extends in an axial direction; a pair of bearings which support the steam turbine rotor in such a way as to be capable of rotating about the axial direction; a steam turbine casing which encloses the steam turbine rotor between the pair of bearings; a casing support unit which supports the steam turbine casing from below; and a first heating unit: which is provided on the casing support unit and which is capable of heating the casing support unit.