An illumination device includes: an optical element which including a hologram recording medium including a first zone and a second zone and can reproduce an image of a scattering plate; an irradiation device which irradiates the optical element with a coherent light beam such that the light beam is allowed to scan the hologram recording medium; and a polarization control unit provided on an optical path of the light beam to an illuminated zone. The light beams incident on respective positions of the hologram recording medium are allowed to reproduce the image superimposed on the illuminated zone. The polarization control unit controls polarization of the light beams such that the light beam incident on the first zone to travel toward the illuminated zone and the light beam incident on the second zone to travel toward the illuminated zone are configured with different polarization components.