A nonaqueous electrolyte secondary battery separator having excellent impact absorbency includes a polyolefin porous film having a full width W at half maximum of a peak of an MD component of not less than 30 degrees. The full width W at half maximum of the peak of the MD component is calculated from an azimuthal profile of a scattering peak on a plane obtained by wide-angle X-ray scattering measurement that is carried out by irradiating a surface of the polyolefin porous film with an X-ray from a direction vertical to the surface of the polyolefin porous film, and/or having a maximum-to-minimum intensity ratio r of not more than 3.6. The maximum-to-minimum intensity ratio r is calculated from a Fourier transformed azimuthal profile obtained by observing the surface of the polyolefin porous film by SEM.