A nonaqueous electrolyte secondary battery insulating porous layer which has an excellent discharge output characteristic is provided. The insulating porous layer is arranged such that an aspect ratio of a projection image of an inorganic filler at a surface of the insulating porous layer is in a range of 1.4 to 4.0 and respective peak intensities I(hkl) and I(abc) of any diffraction planes (hkl) and (abc) of the insulating porous layer satisfy the following Formula (1). The peak intensities obtained from the diffraction planes (hkl) and (abc) orthogonal to each other are measured using a wide-angle X-ray diffraction method, and a maximum value of the peak intensity ratio is in a range of 1.5 to 300 when calculated by the following Formula (2): I(hkl)>I(abc)  (1) I(hkl)/I(abc)  (2).