According to one embodiment, an illumination device comprises a first mounting board including a plurality of first light emitting elements, a second mounting board including a plurality of second light emitting elements, and a first wiring board including a first wiring line electrically connected to at least one of the plurality of first light emitting elements and the plurality of second light emitting elements. The first mounting board and the second mounting board extend in a first direction and are arranged along a second direction intersecting the first direction. The first wiring board is superposed on the first mounting board and the second mounting board. The first wiring board has rigidity that is lower than rigidity of each of the first mounting board and the second mounting board.