An illumination device including a base, at least one LED light source and a first diffusing element is provided. The base has a supporting plane. The LED light source disposed on the supporting plane has a light emitting surface substantially parallel to the supporting plane. The first diffusing element disposed on the supporting plane is a hollow column surrounding the LED light source. An inner diameter width of the first diffusing element is gradually reduced outward from the base. The first diffusing element has a rough surface comprising a plurality of surface structures.