The present invention provides an aggregate of nanofibers having less spread of single fiber fineness values that can be used in wide applications without limitation to the shape and the kind of the polymer, and a method for manufacturing the same. The present invention is an aggregate of nanofibers made of a thermoplastic polymer having single fiber fineness by number average in a range from 1 x 10 to 2 x 10 dtex and single fibers of 60% or more in fineness ratio have single fiber fineness in a range from 1 x 10 to 2 x 10 dtex.