An illumination apparatus for planar display devices, including an optical element for making light travel parallel to an optical axis, is provided. The illumination apparatus includes a dot light source for radiating light, and a light guide plate having the optical element. The optical element is composed of a first refraction facet, which is adjacent to the dot light source and increases the emission angle of the light, and a second refraction facet, which is isolated a predetermined distance from the first refraction facet while facing the first refraction facet and reduces the emission angle of the light. In this structure, the light travels parallel to the optical axis. In the illumination apparatus, the emission angle of incident light is reduced, preferably, the light travels parallel to the optical axis. Therefore, areas not reached by light, between adjacent dot light sources, are eliminated, and light is uniformly incident upon a hologram so that the luminance and intensity of light emitted from the light guide plate are uniformly distributed.