To provide a reprocessing method for spent nuclear fuel allowing to produce UO3 product powder and UO2/PuO2 product powder without requiring complex devices and works including a fluidized bed denitrating device, a microwave denitrating device, and an enriching device.

Uranyl nitrate/plutonium nitrate mixture 1 after co- decontamination is pressurized and heated to a supercritical or subcritical pressure and temperature to recover a part of uranium as UO3 by deposition thereof, and the residual uranyl nitrate/plutonium nitrate mixture 1 is pressurized and heated to a pressure and temperature different from the pressure and temperature above to recover UO3/PuO2 mixture by deposition thereof.