A waveguide corner including a first rectangular waveguide and a second rectangular waveguide. An end face of the second rectangular waveguide is made open to an H-plane wall of the first rectangular waveguide and the H-plane walls of the second rectangular waveguide are disposed along the pipe axis of the first rectangular waveguide. Accordingly, planes of polarization of electromagnetic waves being propagated in the first and second rectangular waveguides are made perpendicular to each other.