A battery separator includes a polyolefin microporous membrane having a width of 100 mm or more, and a porous layer laminated on at least one surface of the polyolefin microporous membrane. The polyolefin microporous membrane has a variation range of an F25 value in a width direction of 1 MPa or less, and the F25 value indicates a value obtained by dividing a load value measured at 25% elongation of a specimen with use of a tensile tester by a cross-sectional area of the specimen. The porous layer contains a fluorine-based resin and an inorganic particle.