PURPOSE: To obtain the title nonwoven fabric useful as filter, etc., having excellent adsorption properties, by blending and dispersing specific glass fibers and thermally meltable synthetic fibers into a specific dispersion medium, drying to give nonwoven fabric of phase separated glass fibers, then heat-treating the nonwoven fabric and treating with an acid.

CONSTITUTION: Glass fibers which are separated into phases of silica phase and acid-soluble phase by heat treatment at 550-800°C, having 4-15mm length and thermally meltable synthetic fibers which are composed of a thermally softening resin such as polyethylene, having 4-15mm length are blended and dispersed in a dispersion medium containing 0.5-5wt.% water-soluble binder such as hydroxyethyl cellulose. The dispersion medium is removed by a filtering wire net and the resulting material is dried to give nonwoven fabric of phase- separated glass fibers. Then the nonwoven fabric is heated (100-120°C), the synthetic fibers are melted, the glass fibers are partially fused each other, immersed in 0.2-6N hydrochloric acid, etc., treated with an acid, the acid-soluble phase is eluted, the woven fabric is washed with water and dried to give the objective nonwoven fabric.