An illumination device, a headlight, and a movable body are provided which can increase luminosity and resolution at a central region or a peripheral region in an illuminable region. A primary lens is placed at a light emission side of a plurality of light sources, and the primary lens includes a plurality of light guides corresponding in a one-to-one relationship to the plurality of light sources. A size of a light exit surface of a light guide corresponding to a light source which illuminates a central region in the illuminable region of the headlight is set to differ from a size of a light exit surface of a light guide corresponding to a light source which illuminates a peripheral region surrounding the central region.