Disclosed are an apparatus and a method for manufacturing composite nanoparticles. The apparatus comprises: a first precursor supply unit vaporizing a first precursor and supplying it to a reaction unit; a second precursor supply unit vaporizing a second precursor and supplying it to the reaction unit; the reaction unit producing composite nanoparticles by reacting the vaporized first precursor with the vaporized second precursor; an oxygen supply line supplying an oxygen source to the reaction unit; and a collection unit collecting the composite nanoparticles produced by the reaction unit. Since gas phase synthesis occurs in different stages using the U-shaped reaction chamber, aggregation is prevented and composite nanoparticles of uniform size and high specific surface area can be produced easily.