To provide a steam pressure-temperature reducing apparatus capable of simultaneously reducing the pressure and temperature of steam to prescribed values.

A steam supply pipe 2 is connected to a turbine 1. A rotational resistance adjusting means 3 is connected to the outside of the turbine 1. A pressure sensor 4 and a temperature sensor 5 are mounted to a steam outlet pipe 10 of the turbine 1. The respective sensors 4, 5 are electrically connected to the rotational resistance adjusting means 3 through a control part 6. The steam outlet pipe 10 is branched and connected to a thermomagnetic engine 8 and a jacket part 15 of a reaction furnace 9. An arbitrary rotational resistance value is set by the rotational resistance adjusting means 3, and the energy of steam supplied from the steam supply pipe 2 is consumed by a prescribed quantity to reduce the pressure and temperature of steam to the prescribed values.