NOVELTY - A porous film separator consists of a separator base material, a porous film formed on at least one surface of the separator base material, and a contact bonding layer provided on the porous film. The porous film contains non-electroconductive particles and water-soluble maleimide-maleic acid copolymer containing structural unit (a) (I), and structural unit (b) (II). The contact bonding layer contains a particulate polymer having glass transition temperature of 10-110 degrees C.    USE - Porous film separator is used for secondary battery (claimed) e.g. lithium ion secondary battery for electronics and motor vehicle.    ADVANTAGE - The porous film separator has excellent heat resistant contractility, blocking resistance and adhesiveness with respect to electrode. The secondary battery containing porous film separator has excellent cycle characteristics and suppressed expansion of battery, and is safe.    DETAILED DESCRIPTION - A porous film separator consists of a separator base material, a porous film formed on at least one surface of the separator base material, and a contact bonding layer provided on the porous film. The porous film contains non-electroconductive particles and water-soluble maleimide-maleic acid copolymer containing structural unit (a) of formula (I), and structural unit (b) of formula (II). The contact bonding layer contains a particulate polymer having glass transition temperature of 10-110 degrees C.    R1=H, 1-6C alkyl, 3-12C cycloalkyl, hydroxyphenyl or phenyl optionally substituted by 1-6C alkyl, 1-6C alkyloxy, or halo;and    X=maleic acid unit which is partially neutralized with ion (other than H ion), partially anhydride or partially esterified.    An INDEPENDENT CLAIM is included for manufacture of porous film separator, which involves coating a slurry containing maleimide-maleic acid copolymer and non-electroconductive particles, on surface of the separator base material, drying and forming the porous film, coating a slurry containing particulate polymer, on porous film, drying, and forming the contact bonding layer.