The present invention provides a separator and a method for manufacturing the separator. The separator includes a first nanofiber layer (20) which has a lattice shape when viewed from a plan view, a second nanofiber layer (30) which is provided on a first surface of the first nanofiber layer (20) and is thinner than the first nanofiber layer, and a third nanofiber layer (40) which is provided on a second surface of the first nanofiber layer and is thinner than the first nanofiber layer. The thickness of the first nanofiber layer ranges from 7 μm to 30 μm. The thickness of each of the second and third nanofiber layers ranges from 1 μm to 5 μm. The present invention can provide a separator which has high insulation, high dendrite resistance, high ion conductivity and high mechanical strength.