NOVELTY - Microporous polyethylene composite film, having a microporous organic/inorganic composite coated layer, is claimed, where: the coated layer is formed on at least one side of the microporous polyethylene film by using a heat resistant resin of melting temperature or glass transition temperature of 170-500 degrees C and inorganic particles; the permeability (Gurley) of overall composite film comprising the coated layer is not more than 300 seconds; and shrinkage after 150 degrees C for 1 hour is 0-3% in both machine direction (MD)/transverse direction (TD).    USE - The microporous polyethylene composite film is useful: in a separator for a battery device, which is a lithium ion battery or fuel cell (all claimed); filters for separation; and membrane for microfiltration.    ADVANTAGE - The composite film has excellent chemical stability and physical properties, excellent stability at high temperature and excellent permeability, thus ensures reliability and efficiency of a battery at the same time. The film exhibits uniform heat resistance and homogeneity of quality. The separator has high power/high capacity.    DETAILED DESCRIPTION - Microporous polyethylene composite film, having a microporous organic/inorganic composite coated layer, is claimed, where: the coated layer is formed on at least one side of the microporous polyethylene film by using a heat resistant resin of melting temperature or glass transition temperature of 170-500 degrees C and inorganic particles; the permeability (Gurley) of overall composite film comprising the coated layer is not more than 300 seconds; shrinkage after 150 degrees C for 1 hour is 0-3% in both machine direction (MD)/transverse direction (TD); maximum thermo mechanical analysis (TMA) shrinkage is not more than 3%; and meltdown temperature is 145-200 degrees C. INDEPENDENT CLAIMS are included for:    (1) preparing highly heat resistant porous coated layer comprising mixing and dissolving a heat resistant resin in a solvent, dispersing the inorganic particles in the solution obtained above to obtain a mixed solution, applying the mixed solution on one or both side of the surface of microporous polyethylene film and drying residual solvent from the formed coated layer;    (2) a separator, for a battery, comprising the above microporous polyethylene composite film; and    (3) a battery device comprising the above separator.    DESCRIPTION OF DRAWING(S) - The diagram shows an electron microphotograph (x 10000) of a surface of the microporous polyethylene composite film.