PURPOSE: To obtain a filter whose occupancy area at the time of in corporating it into a hybrid integrated circuit is small and which can obtain a sufficiently low cut-off frequency by providing a metallic layer and a ferromagnetic material layer directly formed on the metallic layer on a conductor signal line.

CONSTITUTION: The metallic layer 4 which is formed on the conductor signal line 2 through an insulating material layer 3, which is thinner than the skin depth of a using frequency and which is grounded and the ferromagnetic material layer 5 formed on the metallic layer 4 are provided. The conductor signal line 2 and the metallic layer 4 form a micro strip line. As the metallic layer 4 is formed more thinly than the skin depth of the using frequency, an electric field induced on the metallic layer 4 by a signal on the conductor signal line 2 is affected by the ferromagnetic material layer 5 and an inductance is generated at the conductor signal layer 2. Furthermore as the metallic layer 4 is grounded, capacitance is generated between the conductor signal line 2 and the metallic layer 4 and the low pass filter of the sufficiently low cut-off frequency is obtained.