Abstract: A method for homogeneously mixing a uranium/plutonium mixed oxide which is used for the preparation of a uranium/plutonium mixed oxide fuel. The method comprises weighing a uranium oxide powder, a plutonium oxide powder, and a dry recovered powder prepared by grinding a uranium/plutonium mixed oxide sinter so as to give a predetermined plutonium enrichment; roughly mixing these powders together by means of a mixer; pulverizing and homogeneously mixing the roughly mixed powder by means of a jet mill; discharging the homogeneously mixed powder together with compressed air from the jet mill; and separating the mixed powder from the air by means of a first-stage cyclone to recover at least 90% of the discharged powder.