PURPOSE: To improve varnishing coil ends and slots by, impregnating un- impregnated part while dripping varnish in such a way that it will not flow out of coil ends, and keep rotating an iron core until such varnish gets.

CONSTITUTION: An iron core 1, pre-heated in a heating furnace, is mounted on a support 3 and is than fitted to a rotating unit at an angle 5° to 10° to a horizontal plane. Then, the iron core 1 is rotated at 10 rpm, and each of the inside and outside periphery of the upper side coil end 2 is provided with three nozzles 5, through which varnish 6 is dripped onto the end of the coil 2. After varnish has flowed out through the other end of the coil 2, the iron core 1 is kept horizontal and rotating until the dripped varnish 6 gels. After the dripped varnish has gelled, the nozzles 5 are located at the inside and outside peripheries of both coil ends and varnish 6 is dripped to impregnate the coils. After enough varnish has been dripped, the coil 2 is heated, while being rotated, at 130°C for 5 hours to cure varnish in a hot-blast drying furnace with its gel.