An illumination device comprising: a plurality of pairs of a light source and a light guide plate, the light guide plate receiving light from the light source, diffusing the light, and performing surface emission of the light, the light guide plate including: a light-emitting section having a light-emitting surface from which the light is emitted; and a light guide section for guiding, to the light-emitting section, the light from the light source, the light guide plates being adjacent to one another in such a manner that a light-emitting section of one light guide plate on one side is disposed on a front surface of a light guide section of a light guide plate adjacent thereto on the other side, wherein: the light-emitting surface includes: a parallel surface parallel to an irradiation object; and a slant surface slanted relative to the irradiation object, the slant surface being provided so as to connect the parallel surface and the front surface of the light guide section of the light guide plate, the illumination device being characterised in that the slant surface has gradients varying continuously relative to the parallel surface in such a manner as to form a curved surface continuously connected with the parallel surface; and the light is emitted from the parallel surface and the slant surface. a plurality of pairs of a light source and a light guide plate, the light guide plate receiving light from the light source, diffusing the light, and performing surface emission of the light, the light guide plate including: a light-emitting section having a light-emitting surface from which the light is emitted; and a light guide section for guiding, to the light-emitting section, the light from the light source, the light guide plates being adjacent to one another in such a manner that a light-emitting section of one light guide plate on one side is disposed on a front surface of a light guide section of a light guide plate adjacent thereto on the other side, a light-emitting section having a light-emitting surface from which the light is emitted; and a light guide section for guiding, to the light-emitting section, the light from the light source, the light guide plates being adjacent to one another in such a manner that a light-emitting section of one light guide plate on one side is disposed on a front surface of a light guide section of a light guide plate adjacent thereto on the other side, wherein: the light-emitting surface includes: a parallel surface parallel to an irradiation object; and a slant surface slanted relative to the irradiation object, the slant surface being provided so as to connect the parallel surface and the front surface of the light guide section of the light guide plate, the illumination device being characterised in that the slant surface has gradients varying continuously relative to the parallel surface in such a manner as to form a curved surface continuously connected with the parallel surface; and the light is emitted from the parallel surface and the slant surface. the light-emitting surface includes: a parallel surface parallel to an irradiation object; and a slant surface slanted relative to the irradiation object, the slant surface being provided so as to connect the parallel surface and the front surface of the light guide section of the light guide plate, the illumination device being characterised in that the slant surface has gradients varying continuously relative to the parallel surface in such a manner as to form a curved surface continuously connected with the parallel surface; and the light is emitted from the parallel surface and the slant surface. a parallel surface parallel to an irradiation object; and a slant surface slanted relative to the irradiation object, the slant surface being provided so as to connect the parallel surface and the front surface of the light guide section of the light guide plate, the illumination device being characterised in that the slant surface has gradients varying continuously relative to the parallel surface in such a manner as to form a curved surface continuously connected with the parallel surface; and the light is emitted from the parallel surface and the slant surface.