An illumination device including a base, a light bar, and a cover is provided. The base has a cavity. The light bar is disposed at the bottom of the cavity and includes a plurality of dot light sources arranged along a first axial direction. The cover is assembled to the base for correspondingly covering the light bar and has a plurality of openings. The distribution density of the openings increases from a corresponding location of a dot light source towards two opposite ends along the first axial direction. A light source and a light module are also provided. Another illumination device including a base and a plurality of light sources is further provided.