PURPOSE: To effective eliminate even high frequency noise having a high frequency component of several 100MHz such as a radiation noise by connecting a 3-terminal capacitor whose lead terminal is applied externally with a bead core between a line and ground.

CONSTITUTION: A filter unit 16 where a 2-terminal capacitor C11 and 3-terminal capacitors C12, C13 are mounted on a printed circuit board 17 is contained in a metallic case 15, input electrodes 21, 22 of the printed circuit board 17 are soldered to input terminals 11, 12 and output electrodes 23, 24 are soldered to output terminals 13, 14. Further, earth electrodes 27, 28 are soldered to the metallic case 15. A common mode noise from the input terminal 11 to the output terminal 13 is subjected to attenuation by an inductance L1 of the bead core 40a of the 3-terminal capacitor C12, then reaches the electrode 36 of a capacitor unit 38, where the signal is bypassed to ground and the result is attenuated by an inductance L2 of the bead core 40b. The common mode noise from an input terminal 12 to an output terminal 14 is attenuated similarly.