PURPOSE: To improve the inserting loss, reflecting loss and frequency characteristics of an impedance converter by composing the converter of an input first coil, an output second coil, and third coil connected at one end to the second coil and opened at the other end.

CONSTITUTION: Three parallel conductors 20, 30, 40 coated with insulating material, e.g., polyurethane or the like are wound on a toroidal type core 10, the first conductor 40 is connected to input terminals 50, 51, the terminal 50 is soldered to an input terminal pattern 100, and the terminal 51 is connected to a ground pattern 200. Then, a terminal 80 connected with ouput side terminal 71, and two terminals 70, 61 is connected to external circuit patterns 400, 300. The terminal 60 of the thrid conductor 20 is opened. In this manner, an impedance converter having less inserting loss and reflecting loss and preferable frequency characteristics can be obtained.