To provide a heat-resistant filter material capable of filtering dust contained in a high-temperature exhaust gas at 60-200C, for example, discharged from a refuse incinerator, a coal boiler, a metal blast furnace or the like in high collection efficiency, and a method for producing the heat-resistant filter material, and especially to provide a mixed staple excellently reducing an amount of fly waste generated at a roller card part in a nonwoven fabric-producing process, an amount of white pill-shaped waste generated in a needle punching process, and an amount of fiber dropped by shock, and a method for producing a nonwoven fabric thereof.

The mixed staple containing a heat-resistant organic fiber and an inorganic fiber is regulated so that the heat-resistant organic fiber may include at least a fluorine-based fiber comprising a drawn fiber, and the bulk density of the mixed staple may be within the range of 5.5-14.8 kg/m3. The heat-resistant filter material is constituted by using the nonwoven fabric comprising the mixed staple as a filter cloth.