A photo-alignment treatment device for a liquid crystal display panel substrate includes at least one light irradiation mechanism including a light source, a polarizer, and a rotation adjustment mechanism and configured to irradiate a liquid crystal display panel substrate with light emitted from the light source through the polarizer. The device also includes a stage configured to support the liquid crystal display panel substrate thereon. The photo-alignment treatment device is configured to irradiate the liquid crystal display panel substrate with light while moving the liquid crystal display panel substrate or while moving the light source with respect to the liquid crystal display panel substrate. A light irradiation direction with respect to the liquid crystal display panel substrate is parallel to a moving direction of the liquid crystal display panel substrate or a moving direction of the light source. The rotation adjustment mechanism is configured to rotate a polarization axis of the polarizer to adjust an exposure direction on a surface of the liquid crystal display panel substrate to substantially 45° with respect to the light irradiation direction.