Abstract: A magnetic core (2) is formed so as to be vertically thin and segmentable into an upper segment (3) and a lower segment (4). An inner portion (2a) and two outer portions (2b), (2b) of the magnetic core (2) are interconnected so as to form a closed magnetic circuit. A substrate (9) is inserted between the two outer portions (2b), (2b), while the inner portion (2a) is inserted into a through hole (10) of the substrate (9). A scroll pattern coil (11) is formed on each of front surface (9a) and rear surface (9b) of the substrate (9) outside the through hole (10). Further, a bobbinless winding coil (13) is inserted into an annular space between the inner portion (2a) and the through hole (10).