A polarization coupling device includes a polarization combining element. The polarization combining element includes a polarization rotating unit that rotates a polarization direction of a first polarized wave incident on the polarization combining element, and a polarization combining unit that combines the first polarized wave with the polarization direction rotated by the polarization rotating unit and a second polarized wave incident on the polarization combining element with each other, and the polarization rotating unit and the polarization combining unit are integrated with each other. Due to this configuration, the polarization coupling device has an effect where downscaling of the device can be advanced.