PURPOSE: To simplify the winding work, to stabilize the performance and to attain mass-production by providing two drum type cores each having ≥1 winding slot and connecting a terminal board implanted with terminals to both end faces of each drum type core applied with winding.

CONSTITUTION: Coils 2, 3 and coils 5, 6 are provided respectively to winding slots 10, 14 of drum type cores 1, 4, bases 16, 8 provided with terminals 17, 19 are fitted respectively to a side face of flanges 9, 15 of the drum type cores 1, 4, a flange 13 of the drum type core 1 and a flange 11 of the drum type core 4 are fitted so that the winding axes of the drum type cores are on the same axis via a base 12 provided with a terminal 18 and wiring is given to the terminals 17, 18, 19 to form a balun coil. Thus, the variation in the degree of coupling of the coils and the variation in the characteristic impedance of a transmission line transformer are reduced, the variation in the wiring lead length is reduced and mass-production is attained through the structure above.