A polarized light irradiation device of the present disclosure has: a light source unit which continuously emits polarized light; a light shaping unit which shapes the polarized light emitted from the light source unit into a preset shape to irradiate an irradiation target object with the shaped polarized light; a transport mechanism which transports the irradiation target object relative to the light source unit; and an interlocking mechanism which periodically and continuously changes a direction of linearly polarized light applied to the irradiation target object or an azimuthal angle of elliptically polarized light applied to the irradiation target object according to an amount of transport of the irradiation target object relative to the light source unit by the transport mechanism.