In a front light equipped with a light source and a transparent plate emitting light from a light emitting surface which is situated at the reverse side against an observation side surface by conducting light from the light source, the reflection preventive patterns comprising the minute unevennesses 30 for prevention of reflection are formed on the light emitting surface. When a wavelength of visible light with the shortest wavelength among light which is emitted from the light source 24 is .lamda.min, the refractive index of the transparent plate is n1 and the refractive index of air is n0, the period p of the minute unevennesses 30 satisfies the following equation. p<.lamda.min/(n0+n1). Thereby, it can be prevented that the diffracted light is emitted from the reflection preventive patterns (light emitting surface) of the transparent plate.