An illumination device is disclosed including: a plurality of light guide plate units each including a light guide plate and an LED substrate; and a base to which the plurality of light guide plate units are attached so as to be laid over the base. The attachment surface of the base is divided into sections for attaching the light guide plate units so as to lay the light guide plate units over the base and each section is provided with an IC board for driving the corresponding LED substrate and snap-fit engagement portions for fixing the light guide plate unit to the base. A case for covering the back surface of the light guide plate units formed transparently, and the base is also formed transparently.