According to one embodiment of the present invention, a method for producing a sialon phosphor comprises: mixing a silicon precursor and an aluminum precursor and sintering the mixture to form a first sintered body; and mixing the first sintered body and a precursor for an active material and heat-treating the mixture to form a second sintered body. That is, the method for producing a sialon phosphor according to one embodiment of the present invention involves firstly forming the first sintered body serving as a host material to stably ensure a crystal structure, and then mixing the active material and the first sintered body so as to preserve the role of the active material without sacrificing the crystal structure of the first sintered body. Eventually, the active material in the crystal structure of the first sintered body is located in an interstitial site not located in the Si or Al position, thereby preventing the degradation of the crystallinity of the first sintered body. In addition, the crystal structure of the sialon phosphor produced by the above-described method is stable, and the sialon phosphor exhibits superior thermal stability at a high temperature, and therefore the degradation in the efficiency thereof caused by a shortened lifespan thereof is extremely slight even over long-term operation. In addition, the crystal structure of the sialon phosphor in the light-emitting device package comprising the sialon phosphor produced by the above-described method is stable, and therefore the degradation in luminance caused by a degradation of crystallinity may be prevented.