To provide an uranyl nitrate-containing raw liquid preparation device capable of preparing an uranyl nitrate-containing raw liquid having a uniform concentration.

The means for solving the above problem is an uranyl nitrate-containing raw liquid comprising preparation device 1 provided with: a preparation tank body 2 of preparing an uranyl nitrate-containing raw liquid; and a stirring device 3 having a stirring blade 8 rotating with a shaft X1 parallel to the horizontal direction as the center. The stirring blade 8 forms a stirring flow to the whole region of the uranyl nitrate-containing raw liquid in the preparation tank body 2.