An illumination device according to the present invention includes a light output unit having an output end that outputs illumination light a diffusion layer that is disposed in a circumferential direction centered on a predetermined axis and that receives the illumination light from the output end, guides the illumination light while diffusing the illumination light, and outputs the illumination light from a surface thereof and a reflective layer that is provided adjacent to a surface of the diffusion layer at an inner side in a radial direction and that reflects the illumination light outward in the radial direction. The diffusion layer contains a light guide material that guides the illumination light and a diffusion material dispersed and supported in the light guide material.
