An illumination device includes an optical component and a light-emitting module. The optical component includes a light-transmitting body, a first optical unit, and a second optical unit. The first optical unit has a light input surface and a plurality of surrounding structures surrounding the light input surface and arranged in a pattern of concentric circles, and each surrounding structure has a first surrounding surface and a second surrounding surface. The second optical unit has a spiral structure surrounding the light output surface of the light-transmitting body and a surrounding frame surrounding the light output surface of the light-transmitting body and the spiral structure, and a relative height from a topmost surface of the spiral structure to the light output surface of the light-transmitting body is increased gradually from inner to outer. The light-emitting module is disposed under the light input surface of the first optical unit.