The present invention provides a method for producing a zinc sulfide based phosphor by firing a zinc sulfide based phosphor precursor, comprising at least: a first firing step of firing a mixture containing a zinc sulfide based phosphor precursor, sulfur, and a chlorine-containing flux; and a second firing step of further firing the fired product obtained from the first firing step, wherein the first firing step comprises: heating the mixture in an atmosphere wherein an air stream is introduced so that a temperature of the mixture is increased from normal temperature to a transformation temperature at which a crystal system of the phosphor precursor is transformed; when a temperature of the mixture is increased above the transformation temperature, switching the atmosphere to a nitrogen atmosphere and continuing the heating of the mixture; and when the temperature of the mixture reaches a temperature in a range of 1000° C. to 1200° C., inclusive, maintaining the temperature of the mixture at a constant level and thereafter rapidly quenching the mixture and washing the mixture to obtain a fired product; and wherein the second firing step comprises heating in the nitrogen atmosphere the fired product obtained from the first firing step so that the temperature of the fired product is increased from normal temperature to a temperature in a range of 650° C. to 1000° C., inclusive; and when a temperature of the fired product reaches the temperature in the range of 650° C. to 1000° C., inclusive, introducing oxygen while maintaining the temperature of the fired product and thereafter rapidly quenching the fired product and washing the fired product to obtain a zinc sulfide based phosphor. Use of the method of the present invention makes it possible to provide a zinc sulfide based phosphor material suitable for use in the production of an EL device that shows high brightness.