PURPOSE: To make possible efficient manufacture by forming an even insulating layer through the inclined rotation of a blank coil in a fluidized synthetic resin powder while heating the coil by turning on electricity, hardening the insulating layer in a heating furnace, impregnating the coil with a synthetic resin and heardening the coil by heating it.

CONSTITUTION: A conductor part 4 in which a conductor 2 and an inter-layer insulating paper 3 are wound alternately on a core 1 and a collar part 5 are covered by the outermost insulating layer 6 formed in the thickness of 10W15mm by a polyester nonwoven fabric, an aromatic polyamide paper and a polyester mat, etc. After being dried by pre-heating this blank coil 7 is put into, at an angle of 45°C, a powder coating tank 8 where a fluidized synthetic resin composition 8' is in flux due to the inflow of air and the coil is rotated while heating it by the application of an electric current to form a synthetic resin insulating layer 9. After heating the coil 7 to completely harden the insulating layer 9, it is put into an impregnating synthetic resin to impregnate it with the resin. Then the coil is heated to harden it. This requires no metal mold and thus makes the efficient manufacture of a product possible.