The present invention produces a laminated porous film which improves the stability of an aqueous dispersion of a metal oxide without lowering battery characteristics, while having high binding properties and excellent heat resistance. This laminated porous film exhibits excellent characteristics when used as a separator for batteries. This laminated porous film is produced by forming a porous coating layer on at least one outer surface of a resin porous film, which is formed of a single layer or a laminate of a plurality of layers, by applying a coating liquid that contains a metal oxide, a resin binder and a volatile acid thereto and drying the applied coating liquid. The coating liquid is prepared so that the difference between the pH (pH1) of the coating liquid and the pH (pH2) of the coating layer is not less than 2.