To obtain a method recovering uranium as reusable pure uranium dioxide by removing impurity when plutonium is recovered from spent oxide nuclear fuel generated from a nuclear power station.

Spent nuclear oxide fuel and reducing agent sample 1a are chlorinated by blowing in chloric gas, into the molten salt dissolved by chloride of produced uranium and plutonium, liquid metal such as cadmium is contacted to extract and remove rare impurity elements, mixture gas of chlorine and oxygen is blown in the molten salt to make uranium be oxychloride and the uranium is sampled to recover pure uranium dioxide.