The present invention aims at providing a blue-aimed phosphor powder which is more excellent in emission characteristic than the conventional rare-earth activated sialon phosphors and which is more excellent in durability than the conventional oxide phosphors.The solving means resides in: firing a starting material mixture in a nitrogen atmosphere at a temperature range between 1,500.degree. C. inclusive and 2,200.degree. C. inclusive, wherein the starting material mixture is a mixture of metallic compounds, and is capable of constituting a composition comprising M, A, Si, Al, O, and N (M is one kind or two or more kinds of element(s) selected from Mn, Ce, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm, and Yb; and A is one kind or two or more kinds of element(s) selected from C, Si, Ge, Sn, B, Ga, In, Mg, Ca, Sr, Ba, Sc, Y, La, Gd, Lu, Ti, Zr, Hf, Ta, and W) by firing; to obtain a phosphor which emits fluorescence having a peak at a wavelength within a range of 400 nm to 700 nm, by irradiation of an excitation source.