A manufacturing method for a Y.sub.2 O.sub.3 : Eu red phosphor is disclosed in which yttrium oxide and europium oxide are used, and also a composite flux composed of a mixture of Na.sub.2 CO.sub.3, NaF and B.sub.2 O.sub.3 is used. The Y.sub.2 O.sub.3 : Eu red phosphor according to the present invention is uniform in its particle size distribution, has a desirable spherical particle shape, shows a perfect filling state of the layer, and shows a luminance improvement by 4-7% over that of the conventional phosphor.