A light emitting device includes a light guide plate and a light source. The light guide plate has a first surface, a second surface that is opposite to the first surface, at least one third surface, and a light incident surface. The third surface and the light incident surface are between the first and second surfaces. The third surface is adjacent to the light incident surface and has a concave-convex structure. The light source is located on the light incident surface. When the light source emits light, the light of the light source enters the light guide plate and transmits to the concave-convex structure, such that the light irradiates out from the concave-convex structure due to refraction, and is reflected back to the light guide plate by the concave-convex structure.