A light diffusing plate integrally formed with an optical element array on the front and rear surfaces thereof, and a direct lighting device having this light diffusing plate installed on a light reflection plate having a box type shape and provided therein with a light source, whereby a light diffusing plate and a thin direct lighting device are provided which eliminate luminance non-uniformity among a number of light sources (inter-light-sources distance) at a practical level (making luminance uniform), and realize higher luminance (delivering luminance equal to that when conventional prism sheets are laminated).