An optical lens for adjusting viewing angle of and diffusing light emitted from a light emitting diode includes a light incident surface and a light emitting surface. The light incident surface is cone-shaped and concave towards the light emitting surface. The light emitting surface is cone-shaped and concave towards the light incident surface. A plurality of annular protrusions is formed on the light incident surface. The annular protrusions are coaxial and a center of each of the annular protrusions is located at an optical axis passing through a vertex of the light emitting surface and a vertex of the light incident surface. A lighting device having the optical lens and the light emitting diode is also provided.