The present invention relates to a method for producing a silicon nitride composite, the method comprising: (S1) a step for mixing an amorphous silicon nitride powder and a reducing agent powder; and (S2) a step for crystallizing at least a portion of the silicon contained in the amorphous silicon nitride by heat-treating the mixed powder. The method can be used to produce the silicon nitride composite at a low cost using a simple process. The silicon nitride composite produced by the method has both a crystalline portion and an amorphous portion, and thus can improve capacity, rate capability, and lifespan characteristics when used as a negative electrode for a lithium secondary battery.
