PURPOSE: To obtain the high reliability against creeping discharge and dielectric breakdown by providing a protective layer such as silicon rubber which is different from an insulating material or a forming material insulating each winding and between the windings around the region where a lead wire from each winding is taken out.

CONSTITUTION: An iron core is inserted inside a bobbin 1, the primary winding 2 made of a polyurethane insulated wire is wound around the bobbin and after an insulating layer 6 made of epoxy resin, etc. is formed, the secondary winding 3 made of the polyurethane insulated wire is wound. Lead wires 4 and 5 are taken out from the primary winding 2 and the secondary winding 3. An insulating layer 7 made of epoxy resin, etc. is formed on the secondary winding 3. A silicon rubber protective layer 8 is provided around the region where the lead wires 4 and 5 are taken out in and around the radial directions in which the lead wires 4 and 5 are taken out.