An object of the present invention is to provide a light diffuser plate (1) which can illuminate the front side more brightly when incorporated in a surface light source (3) constituting a transmissive image display (2).The light diffuser plate of the present invention comprises a transparent resin and a light diffuser dispersed in the transparent resin, wherein the transparent resin is a transparent resin which has a light transmittance [T.sub.600] at a wavelength of 600 nm of 85% or more measured with respect to a thickness of a 2 mm thick plate-shaped specimen, and a ratio [T.sub.365/T.sub.600] of a light transmittance [T.sub.365] at a wavelength of 365 nm to the light transmittance [T.sub.600] is 0.90 to 0.99. The transparent resin is polystyrene or the like, an average particle diameter of the light diffuser is from 0.5 to 5 .mu.m, an absolute value [|.DELTA.n|] of a difference in a refractive index between the light diffuser and the transparent resin is 0.05 or more, an amount of the light diffuser is from 0.1 to 10 parts by mass based on 100 parts by mass of the transparent resin, and the light diffuser plate has a thickness within a range of from 1 to 5 mm.