To provide an orthogonal polarization coupler with can realize satisfactory circulaly polarized characteristics, when a circularly polarizes wave is generated.

This polarized coupler consists of a circular waveguide 10, which is connected to a horn 1 at one of its both ends and rectangular waveguides 21a and 21b which are connected to the side face of the waveguide 10. That is, rectilinear parts 22a and 22b of waveguides 21a and 21b are connected vertically to the side face that is set on the same circumference of the waveguide 10. The angle θ1 formed between both parts 22a and 22b is set to 80 degrees. In addition, the coupling holes Va and Hb are formed on the side face of the waveguide 10 to secure linkage to the waveguides 21a and 21b respectively. At the inside of the waveguide 10, the polarized wave that is excited through the waveguide 21a and rotated by the effects of the hole Hb is approximately orthogonal to the polarized wave that is excited through the waveguide 21b and rotated by the effects of the hole Va.