Disclosed is a method for producing a cerium dioxide nanopowder by flame spray pyrolysis. The method comprises dissolving a cerium compound in an organic solvent to prepare a precursor solution, atomizing the precursor solution into microdroplets using an ultrasonic atomizer, transferring the microdroplets together with an argon gas as a carrier gas to a central portion of a high-temperature diffusion flame burner, subjecting the microdroplets to pyrolysis and oxidation in the central portion of the diffusion flame burner to produce a cerium dioxide nanopowder, and collecting the cerium dioxide nanopowder using a collector. According to the method, a cerium dioxide nanopowder can be continuously produced on a large scale by flame spray pyrolysis. In addition, the particle size and uniformity of the cerium dioxide nanopowder can be controlled by appropriately selecting the kind of the solvent and the concentration of the raw material. Furthermore, flame spray pyrolysis allows the cerium dioxide to have a fluorite crystal structure.