A separator is disclosed which enables to inject a non-aqueous electrolytic solution easily during production of batteries such as lithium ion secondary batteries and also enables to produce a battery which is excellent in various battery performances.The battery separator comprises a long porous film in which plural non-porous linear regions are arranged in a width direction of the film, at least one surface of the linear regions being a concave or convex surface is advantageously used as a battery separator for lithium secondary batteries or the like.