disclosed is a method for preparing a fluorescent substance , which is represented by the formula m 1 - z eu z si a o b n c , and the present invention provides the method for preparing a nitride - based fluorescent substance comprising the following steps : a preliminary firing step further comprising a first firing step of creating a first firing product by mixing and firing a first precursor group including an m precursor and a first silicon precursor , and a second firing step of creating a second firing product by mixing and firing a second precursor group including an eu precursor and a second silicon precursor ; and a secondary firing step of mixing and firing the first firing product and the second firing product .