An intermediate-pressure turbine is divided into a high-temperature, high-pressure side high-temperature, intermediate-pressure turbine section 11a and a low-temperature, low-pressure side low-temperature, intermediate-pressure turbine section 11b, the component members of the high-temperature, intermediate-pressure turbine section 11a are formed of austenitic heat-resistant steels or Ni-based alloys, and the high-temperature, intermediate-pressure turbine section 11a is operated by steam having a temperature of 650° C. or more. Other turbines are mainly formed of ferritic heat-resistant steels. Thus, a steam turbine power plant having high thermal efficiency and being economical can be provided.