A battery separator which comprises a porous base containing at least one member selected from a nonwoven fabric or a paper, the nonwoven fabric and the paper containing an organic fiber fibrillated to a fiber diameter of 1 μm or less, and an organometallic compound impregnated, coated or sprayed to the porous base, the resulting separator being for non-aqueous electrolyte batteries, the nonwoven fabric and the paper being made by wet paper making process, and wherein the porous base has a maximum pore diameter of 20 μm or less as measured by bubble point method specified in ASTM F-316-80.