To provide a light transmitting plate which emits the light with excellent uniformity of brightness in the direction advantageous to visibility and is excellent in utilization efficiency of the light by specifying the projected area of an opening width to an emitting surface in bottom surface of a prism-shaped recessed part, constituting the prism-phased recessed part of a light taking-out inclined face inclined at a specific angle and a back face, and specifying an inclination of a transmitting surface to the emitting surface.

This light transmitting plate is composed of a plate-like material having an emitting surface 11, a bottom surface 12 opposed to it and an incident surface composed of the emitting surface 11 and a side end surface of a bottom surface 12. A prism-shaped recessed part 21 in the direction running along the incident surface and a transmitting surface 33 composed of a bottom surface are periodically provided on its bottom surface 12, and the projected area of an opening width to the emitting surface 11 in the bottom surface of its prism-shaped recessed part 21, is set 1/5 or smaller of that of the transmitting surface 33. The prism-shaped recessed part 21 is composed of a light taking-out inclined face 31 inclined to the incident surface side from the apex at an angle of 30 to 48 degrees with the emitting surface 11 as a reference and a back face 32 inclined at an angle not less than 60 degrees. An inclination of the transmitting surface 33 to the emitting surface 11 is set not more than 8 degrees.