A light guide plate having a multi-periodic micro pattern, which can minimize chromatic dispersion, and an illumination apparatus for a display device employing the light guide plate are provided. The light guide plate includes a top surface and a micro pattern formed on the top surface and allowing light, which is incident from a first side surface of the light guide plate, to be emitted from the top surface. The micro pattern is a combination of at least two periodic patterns having different periods to reduce chromatic dispersion of light emitted from the top surface.