Provided is a separator free of destruction of a release layer due to expansion and/or contraction of the substrate, and unsusceptible to wrinkles.
A separator 1 containing a substrate 2 and a release layer 3 formed on at least one side of the substrate 2, wherein the separator 1 shows a strain of not more than 7% when a load of 5N/20mm is applied for one minute in the pulling direction, and when the substrate 2 is cut in half in the thickness direction to divide the separator 1 into two, an apparent elastic modulus (E1) in the pulling direction of one of the divided separators 1A is larger than an apparent elastic modulus (E2) in the pulling direction of the other divided separator 1B.