Provided is a backlight device having: a light source element having light emitting diodes and a lens expanding light from the light emitting diodes; a housing containing the light source element; a diffuser plate covering an opening portion of the housing; and a reflection sheet reflecting light emitted from the light source element, toward the diffuser plate. In the light source element, a plurality of the lenses are arranged at a central zone, the plurality of lenses being arranged in a plurality of rows.