Abstract: A transformer includes a bobbin having main and auxiliary bobbin regions (11, 12) separated by an intermediate collar (14) and has primary and secondary windings (16, 17) wound around the main bobbin region (11). A part of the primary or secondary windings (16, 17) or a different winding (18) having a small number of turns other than the primary and secondary windings (16, 17) is wound around the auxiliary bobbin region (12). At least one of the primary and secondary windings (16, 17) is prepared from a winding wire having reinforced insulation of a multi-layered structure. One of the primary and secondary windings (16, 17) which is prepared from the winding wire having reinforced insulation has its lead-out ends opposite to each other which are led through the auxiliary bobbin region (12) to terminal pins (8A) and are then soldered thereto.