PURPOSE: To reduce costs and to enhance thinning and characteristics by integrally forming a magnetic substance core part and a terminal supporting part of an insulating magnetic substance, disposing the magnetic substance core part on the terminal supporting part and forming the terminal supporting part so that it has a part extending in parallel to a through hole under the through hole.

CONSTITUTION: A magnetic substance core part 5a and a terminal supporting part 6a are provided in one magnetic substance block 20 comprising the ferrite of an insulating magnetic substance. The magnetic substance block 20 is formed in the shape of a kamaboko (a boiled fishpaste having a semicircular form) and the terminal supporting part 6a is formed in the shape of a plate or a base for the kamaboko, and thereon the magnetic substance core part 5a is disposed. Accordingly, the terminal supporting part 6a functions as a core supporting base. A first and a second through holes 7, 8 are linearly extended from one end surface 21 to the other end surface 22 and at the same time disposed in parallel to each other. The terminal supporting part 6a is disposed under at least the first and the second through holes 7, 8 of the magnetic substance core part 5a.