When lights orbiting around a black hole reach an observation point, they form a photon ring that outlines the black hole shadow. In this talk, we focus on the polarization pattern on a photon ring formed by linearly polarized lights and show how it depends on the spin parameter of the black hole and the inclination angle of the rotation axis. We clarify the relationship between polarization propagation and hidden symmetry in the Kerr spacetime, such as the Killing-Yano symmetry, and consider the gravitational Faraday rotation, which is a rotation of the polarization plane due to the gravitational field during propagation.