Turbine rotor and steam turbine

A turbine rotor includes: a high-temperature turbine rotor constituent part where high-temperature steam passes; low-temperature turbine rotor constituent parts sandwiching and weld-connected to the high-temperature turbine rotor constituent part and made of a material different from a material of the high-temperature turbine rotor constituent part ; and a cooling part cooling the high-temperature turbine rotor constituent part by ejecting cooling steam to a position, of the high-temperature turbine rotor constituent part , near a welded portion between the high-temperature turbine rotor constituent part and the low-temperature turbine rotor constituent part . A value equal to a distance divided by a diameter is equal to or more than 0.3, where the distance is a distance from the position, of the high-temperature turbine rotor constituent part , ejected the cooling steam up to the welded portion , and the diameter is a turbine rotor diameter of the high-temperature turbine rotor constituent part