PURPOSE: To branch two orthogonal polarized waves having a low frequency with no loss branched to a sub-waveguide side by using ≥6 sub-waveguides branched from a common transmission line of a branching filter and employing hybrids being the same number as that of the sub-waveguides.

CONSTITUTION: ≥6 sub-waveguides 5 are provided to a common transmission line 4. Two polarized waves, vertically polarized wave E1 and a horizontally polarized wave E2 orthogonal to each other and having a comparatively low frequency fL are transmitted. The two sub-waveguides 5 at the upper 45° face are combined by the hybrid 6 and the two sub-waveguides 5 at the lower 45° face are combined by the hybrid 6. The outputs of said two terminals are synthesized at two parts by the hybrid 6 further. One of the two outputs and the output of the two upper/lower sub-waveguides 5 combined by the hybrid 6 are synthesized by the hybrid, then an output of the horizontally polarized wave E2 is obtained. Similarly, the outputs of the other and the left and right waveguides are synthesized, then the verticaly polarized wave E1 is obtained.