was 6 kg cm 2 and an applied voltage was 50 kv dc the spinneret on the knife edge constructed as in fig1 was used in the following examples the diameter of the spinning nozzle was 0 25 mm l d of the nozzle was 10 and dcd was varied in examples 1 to 3 and set to 300 mm in examples 4 to 10 the number of the spinning nozzles was 500 the width of a die was 750 mm the nozzle projection u201c e u201d was about 0 to 3 mm and the flow rate of compressed air was maintained at 300 to 3 000 m min through the air nozzle example 1 was good in fluidity and spinning ability but poor in formation of web examples 2 and 3 were good in fluidity spinning ability and formation of web examination of sem pictures showed fiber diameter distribution of about 500 nm to 2 u03bcm in particular example 3 demonstrated uniform fiber diameter distribution in the range of 500 nm to 1 2 u03bcm in comparative example 1 it was difficult to prepare a pan 25 solution and thus no result was obtained table 2 reports conditions and their results of examples 4 to 10 which used nylon 6 6 for polymer and formic acid for solvent the polymer solution concentrations were 25 fiber diameter distributions in table 2 were determined by sem picture examination in which nanofibers having uniform diameters are irregularly arranged in the form of.