PURPOSE: To provide a new wool filter for dust-proof masks which is produced by blending synthetic resin film-slit fibers with wool fibers, and to provide its production method.

CONSTITUTION: This wool filer is produced by randomly and uniformly blending 40-90 wt.% wool fibers, particularly far infrared radiation-antibacterial and deodorant wool fibers with 10-60 wt.% synthetic resin film-slit fibers, preferably polyolefin resin film-slit fibers, and forming into a thick nonwoven using this blend. The obtained filter foes not contain any chemicals, has low resistance to sucking and exhausting air and good collection efficiency of fine particles and is contributed to health and disease prevention for its wearing person. The filter is useful at the site of coal mining, at the site of the shipbuilding industry or the steel industry, at the site of the milling industry or the textile industry, at the cement construction site, as various painting sites, or the like.