The present invention enables stable mass production of nanofibers having desired performance. The field emission device (20) is equipped with a conductive case (100), a collector (150) fitted on the case (100) through an insulation member (152), a nozzle block (110) having a plurality of nozzles (112), the nozzle block placed so as to face the collector (150), a power device (160) for permitting high voltage between the nozzle block (110) and the collector, an auxiliary belt placed in a position that encircles the collector, and an auxiliary belt driving device (174) for rotating the auxiliary belt according to the transfer speed, wherein the power device (160) has an electrode on one side of positive/negative electrodes that connects to the collector (150), and an electrode on the other side that connects to the nozzle block (110) and the case (100), and the insulation member (152); has the outer circumference thereof located on the outer side than the outer circumference of the collector, wherein the thickness (a) of the insulation member satisfies a >= 6 mm, and when calling the distance between the outer circumference of the insulation member (152) and the outer circumference of the collector (150), b, a+b >= 50 mm is satisfied.