An optical plate includes a plurality of light-guiding elements. The optical plate includes a first optical surface which a light is incident to and a second optical surface which the light goes out from. The plurality of light-guiding elements disposed on the third optical surface are used for guiding the light incident to the first optical surface. Each light-guiding element includes a first arc portion, a second arc portion, and a third arc portion. Both first ends of the first arc portion and the second arc portion are connected with a first portion of the third arc portion, and a second end of the first arc portion is connected to a second portion of the second arc portion. Each light-guiding element is substantially spiral-shaped.