Disclosed is a microporous high density polyethylene film for a battery separator and a method of producing the same. The microporous high density polyethylene film includes high density polyethylene with a weight average molecular weight of 2.times.10.sup.5-5.times.10.sup.5, containing 5 wt % or less molecule with a molecular weight of 1.times.10.sup.4 or less. The microporous high density polyethylene film has tensile strengths of 1,100 kg/cm.sup.2 or more in transverse and machine directions respectively, a puncture strength of 0.22 N/.mu.m or more, a gas permeability (Darcy's permeability constant) of 1.3.times.10.sup.-5 Darcy or more, and shrinkages of 5% or less in machine and transverse directions, respectively. Particularly, the microporous high density polyethylene film has an excellent extrusion-compoundabiliy and stretchability and a high productivity, and can improve the performances and stability of a battery produced using the same.