An illumination device includes a light diffusion device including element diffusion devices that diffuse incident light, a coherent light source that emits coherent light, a shaping optical system that shapes the coherent light, a scanner that adjusts a traveling direction of the coherent light so as to allow the coherent light to scan the light diffusion device, and a light condensing optical system located on a light path of the coherent light from the shaping optical system up to the light diffusion device. The light condensing optical system condenses the coherent light such that a spot area on the light diffusion device is smaller than the element diffusion device. Each element diffusion device diffuses the coherent light incident thereon so as to illuminate an element illumination area corresponding to the element diffusion device.