To provide a nonwoven fabric having many fine spaces, capable of achieving battery capacity increase and thinning the film, and excellent in shut down performance, and to provide a separator for secondary batteries, made of the nonwoven fabric.

There is provided the nonwoven fabric containing 0.5 mass% or more of nanofibers having an average fiber diameter of 10-3,000 nm, wherein an acid modified polyolefin resin is contained in the nonwoven fabric and the content of the acid modified polyolefin resin is 0.1-95 mass%. There is also provided a nonwoven fabric whose nanofiber contains polyvinyl alcohol. Further, a separator for secondary batteries is provided which is made from the nonwoven fabric.