Provided is an illumination device (100) including a light output unit (1) having an output end (1a) that outputs illumination light； an optical member (2) that is disposed on a circumference centered on a predetermined axis and that receives the illumination light from the output end (1a) and outputs the illumination light from a surface thereof； and a reflective layer (3) that is provided adjacent to a surface of the optical member (2) at an inner side in a radial direction and that reflects the illumination light outward in the radial direction. The optical member (2) includes a light guide layer (4) that receives the illumination light from the output end (1a) and that guides the illumination light and a diffusion layer (5) that is located outside the light guide layer (4) in the radial direction and at one end of the light guide layer (4) in a direction along the predetermined axis and that receives the illumination light from the light guide layer (4) and guides the illumination light while diffusing the illumination light.
