PURPOSE: To improve sharply a temperature characteristic, by separately winding a winding for excitation and winding for detecting change in magnetic flux around a ferrimagnetic body and ferrimagnetic body yoke, respectively.

CONSTITUTION: A resistance film 3 is vapor deposited on one wide surface of a dielectric body 2 having a specific inductive capacity which is almost equal to that of a ferrimagnetic body 1 and two pieces of dielectric bodies 2 are put together with the resistance film 3 in-between them. After the dielectric bodies 2 and ferrimagnetic body 1 are brought into contact with each other, plated or vapor deposited wave guides 4 are formed on the whole surface of the ferrimagnetic body 1 except both end faces by electroless plating, vapor deposition method, etc., and then, a magnet 5 and ferrimagnetic body yoke 8 are arranged above the wave guides 4. Then a winding for excitation 6 is wound around the ferrimagnetic body 1 and a winding for detecting change in magnetic flux 7 is wound around the ferrimagnetic body yoke 8 and the magnetic flux in the ferrimagnetic body 1 is detected through the ferrimagnetic body yoke 8 under a condition where the winding 7 for detecting change in magnetic flux is not influenced by a magnetic field generated by a pulse current flowing through the winding 6 for excitation.