Abstract: A filter material comprising a nonwoven fabric which comprises an ultra-fine continuous fiber having a mean fiber diameter of 0.05 to 1.8 ?m is prepared by dissolving or eluting a water-soluble thermoplastic resin from a nonwoven fabric or nonwoven web which comprises a conjugate continuous fiber comprising the water-soluble thermoplastic resin and a water-insoluble thermoplastic resin with a hydrophilic solvent and allowing to remain part of the water-soluble thermoplastic resin in the nonwoven fabric or the nonwoven web. In the filter material, the ultra-fine continuous fiber forms a bundle having a mean width of 3 to 100 ?m and the nonwoven fabric has an occupancy area ratio of the bundle of the ultra-fine continuous fiber of 1 to 20% in the surface of the nonwoven fabric. The nonwoven fabric also satisfies the following formula: 100×(B)/(A)?5 wherein (B) is a tensile strength (kgf/5 cm) in each of a longitudinal direction and a width direction of the nonwoven fabric and (A) is a fabric weight (g/m2).