An illumination device comprising: a coherent light source that emits a plurality of coherent light beams; and an optical device that diffuses the plurality of coherent light beams and illuminates a predetermined illumination area, the optical device having a plurality of diffusion regions that illuminate the illumination area by diffusing respective coherent light beams, the diffusion regions being provided corresponding to the plurality of coherent light beams; characterized in that the plurality of diffusion regions have a plurality of element diffusion regions that illuminate partial regions in the illumination area; and the illumination device further comprises a timing control unit that individually controls incident timing of the plurality of coherent light beams to the optical device or illumination timing of the illumination area so that a first region in the illumination area and a second region different from the first region in the illumination area have different illumination modes, respectively, wherein the timing control unit individually controls the incident timing of the plurality of coherent light beams to the optical device or the illumination timing of the illumination area so that - one of the first and second regions is not illuminated and another of the first and second regions is illuminated, or - the first and second regions are illuminated with different colors, or - the first and second regions have different illumination intensities, or - one of the first and second regions has continuous illumination, and another of the first and second regions has flashing illumination. a coherent light source that emits a plurality of coherent light beams; and an optical device that diffuses the plurality of coherent light beams and illuminates a predetermined illumination area, the optical device having a plurality of diffusion regions that illuminate the illumination area by diffusing respective coherent light beams, the diffusion regions being provided corresponding to the plurality of coherent light beams; characterized in that the plurality of diffusion regions have a plurality of element diffusion regions that illuminate partial regions in the illumination area; and the illumination device further comprises a timing control unit that individually controls incident timing of the plurality of coherent light beams to the optical device or illumination timing of the illumination area so that a first region in the illumination area and a second region different from the first region in the illumination area have different illumination modes, respectively, wherein the timing control unit individually controls the incident timing of the plurality of coherent light beams to the optical device or the illumination timing of the illumination area so that - one of the first and second regions is not illuminated and another of the first and second regions is illuminated, or - the first and second regions are illuminated with different colors, or - the first and second regions have different illumination intensities, or - one of the first and second regions has continuous illumination, and another of the first and second regions has flashing illumination. - one of the first and second regions is not illuminated and another of the first and second regions is illuminated, or - the first and second regions are illuminated with different colors, or - the first and second regions have different illumination intensities, or - one of the first and second regions has continuous illumination, and another of the first and second regions has flashing illumination.