Provided is a nonaqueous electrolyte secondary battery separator including a porous film containing, as a main component, polyolefin having a weight average molecular weight of not less than 500,000, the nonaqueous electrolyte secondary battery separator having an MD orientation ratio of 58% to 80%, a degree of MD orientation of 70% to 80%, and a degree of TD orientation of 65% to 85%, the nonaqueous electrolyte secondary battery separator having a film thickness of not more than 14 μm, and the nonaqueous electrolyte secondary battery separator being excellent in shutdown temperature and puncture strength.