To provide a geothermal steam turbine rotor capable of eliminating deterioration of long term durability due to hydrogen embrittlement.

This invented geothermal steam turbine rotor 1 is provided with a rotor shaft 2 having a plurality of blade grooves 3 formed on an outer circumference part and a plurality of moving blades 5 having Christmas tree shape blade legs 6 fitting with the blade grooves at each base part. The blade grooves 3 and the blade legs 6 are covered by anti-corrosion layers 4, 7 against corrosive composition of corrosive liquid of geothermal steam. The anti-corrosion layers 4, 7 include inner anti-corrosion layer 41, 71 of 20μm to 50μm thickness using admixture of thin scale like molybdenum disulfide powder and epoxy resin bonding agent, and outer anti-corrosion layers 42, 72 of 50μm to 100μm thickness arranged in a corrosive composition entrance route side of the inner anti-corrosion layer and using fluororubber resin.