To stably apply an enclosure resin on required parts with good efficiency.

The method comprises immersing an upper flange 4a of a coil component 3 provisionally fixed to a coating jig 13 in a resin to apply this resin 2 to the flange 4a, pushing the coil component 3 into an elastic block 21b of e.g. silicone rubber enough to expand the resin 2 on the flange 4a toward a winding 5 by the elastic block 21b, thereby applying the resin 2 to the lower part of the winding 5, and repeating the above steps several times to gradually expand the resin 2 to the winding 5 until the resin perfectly covers the winding 5.