An illumination device configured to emit illumination light has a light source arranged inside a housing generating the illumination light; a diffusing panel attached to the housing; and a projector arranged inside a space formed by the housing and a part of the diffusing panel for projecting an image onto a projection surface. An optical unit is arranged so that an incident direction of a light flux incident from a display element provided in the projector onto a projection optical system of the projector is substantially vertical or in a direction closer to a vertical direction than a direction parallel to a horizontal plane, or so that an optical axis of the projection optical system on which the light flux from the display element provided in the projector is incident is substantially vertical or in a direction closer to the vertical direction than the direction parallel to the horizontal plane.