PURPOSE:To remove the troubles such as deformation of a winding and the like generating when a soldering process is performed by a method wherein, after the center part of the wound part of an insulated conductive wire has been partially welded, the lead of a lead-out part is solder-dipped, both ends of the wound part in the vicinity of the lead-out part is partially welded using the remaining heat of the above-mentioned welding. CONSTITUTION:After a wound part 16 has been formed by performing a winding process 11, its center part 22 is heated up by the hot air 26 sent from a hot- air generator 25, and the center part 22 is partially welded. The coil-wound part 16 is continuously wound out from a winding machine, and hot air 26 is intermittently blasted, thereby enabling to perform a continuous fusion-welding. A hot air generator 25 supplies clean air sent from the compressor 29 of an air source to the heater 28, which is connected to the voltage regulator 27 with which source voltage is controlled, through a flow-rate limiter 20, and the hot air blows out on the center part 22 of the wound part 16. Then, lead-out parts 17 and 18 are solder-dipped in the solder vessel containing fused solder. In this soldering process, the end parts 20 and 21 of the winding part located in the vicinity of the lead-out parts 17 and 18 can be partially fuse-welded by the remaining heat of the solder-dipping process.