Nonaqueous electrolyte secondary battery porous layer

A nonaqueous electrolyte secondary battery porous layer comprising at least one type of a resin having an amide bond, wherein an aspect ratio of a pore which is represented by Formula (1) is not less than 1.0 and not more than 2.2,

• Aspect ratio of pore=2a/2b Formula (1)
• wherein:
• 2a represents a greatest diameter of a pore in the porous layer;
• and 2b represents, in an ellipsoid obtained by rotating the pore of the porous layer about a central axis which coincides with a greatest diameter, a greatest diameter in a direction perpendicular to the central axis, and
• wherein the at least one type of the resin having the amide bond is a block copolymer including a block A containing, as a main component, units each represented by Formula (2), and a block B containing, as a main component, units each represented by Formula (3):
• —(NH—Ar1—NHCO—Ar2—CO)— Formula (2)
• —(NH—Ar3—NHCO—Ar4—CO)— Formula (3)
• wherein:
• Ar1, Ar2, Ar3, and Ar4 may each vary from unit to unit,
• Ar1, Ar2, Ar3, and Ar4 are each independently a divalent group having one or more aromatic rings,
• not less than 50% of all Ar1 each have a structure in which two aromatic rings are connected by a sulfonyl bond,
• not more than 50% of all Ar3 each have a structure in which two aromatic rings are connected by a sulfonyl bond, and
• 10% to 70% of all Ar1 and Ar3 each have a structure in which two aromatic rings are connected by a sulfonyl bond.