SEPARATOR FOR ELECTRIC STORAGE DEVICE AND ELECTRIC STORAGE DEVICE

The present disclosure provides a separator for an electric storage device, which separator is capable of reducing clogging and has an excellent thermal stability, and an electric storage device using the same. The above-described separator for an electric storage device includes a microporous layer (A) and a microporous layer (B) that contain 70 wt % or more of polypropylene, and the area average major pore diameter in an ND-MD cross section of the microporous layer (B) is not more than 0.95 times the area average major pore diameter in an ND-MD cross section of the microporous layer (A). Alternatively, the separator for an electric storage device contains 70% by weight or more of a polyolefin, and the area average major pore diameter of a first porous surface (X) of the separator is not less than 1.05 times and not more than 10 times the area average major pore diameter of a second porous surface (Y) on the side opposite thereto.