A backlight (illumination device; 2) of the present invention includes: multiple light sources (5); multiple light guide plates (7, 17, . . . ) for causing surface emission of light from the light sources (5); and a diffusing plate (8) for diffusing light from the light guide plates (7, 17, . . . ), the diffusing plate (8) being provided so as to be separate from and face the light guide plates (7, 17, . . . ). Each of the light guide plates (7, 17, . . . ) includes: a light-emitting section (7b) having a light-emitting surface (7a); and a light guide section (7c) for guiding, to the light-emitting section (7b), light from the light sources (5), a light-emitting section (17b) of the first light guide plate (17) being provided above a light guide section (7c) of the second light guide plate (7) adjacent to the first light guide plate (17). A light amount adjusting section (11) for reducing the amount of light incident on it is provided so as to be separate from the diffusing plate (8) and so that the orthogonal projection of the light amount adjusting section (11) onto the light-emitting region covers the boundary between any adjacent light guide plates (7, 17, . . . ). This allows for production of a tandem-type illumination device having further improved luminance uniformity.