Provided is an illumination device for a projection device, which is appropriate to stereoscopic display and allows speckles to be inconspicuous. The illumination device includes: an optical element (50) which including a hologram recording medium (55) including a first zone Z1 and a second zone Z2 and can reproduce an image 5 of a scattering plate 6; an irradiation device (60) 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 (70) provided on an optical path of the light beam to an illuminated zone (LZ). 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 (70) 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.