PURPOSE: To close the ratio of the cut-off frequency of the low pass filter and to that of the high pass filter to 1, by mounting the low pass and high pass filters so that the mutual effect by them can be reduced.

CONSTITUTION: The resonance circuit 11 of the attenuation pole PL1 is provided at the position on and after the second position of the low pass filter 11 by looking from the common terminal pair 13, and the resonance circuit 21 of the attenuation pole PH1 is placed on and after the second position of the high pass filter 12. The resonance circuits of the low pass filter 11 are placed in the order of the circuits 11, 12, 11, 15 from the common terminal pair and in the high pass filter 12, the circuits are placed in the order of the resonance circuits 22, 23, 21. Thus, the mutual effect of both the filters 11 and 12 is less to obtain excellent branching filter performance.