A light guiding plate, characterized by comprising a transparent thermoplastic resin composition containing 1-200 ppm of fine particles having a refractive index of 1.7-3.0 and an average particle diameter of 0.01-1.0 m. This light guiding plate is suitable for display devices used in office automation apparatuses such as personal computers, word processors, etc. and various monitors displaying image signals such as panel monitors, television monitors, etc., display devices used in illuminators for indoor or outdoor space, and signs.