An area light source device, which is disposed between a liquid crystal display panel and a display medium and illuminates the liquid crystal display panel from a back side thereof, includes a light source, a light guide, and a first optical sheet and a second optical sheet which are stacked between the liquid crystal display panel and the light guide and impart predetermined optical characteristics to emission light emerging from the light guide. The first optical sheet is disposed on the liquid crystal display panel side, and the second optical sheet is disposed on the light guide side. The first optical sheet and the second optical sheet have opening parts opposed to the display medium, and the first optical sheet is disposed to cover edges that define the opening part of the second optical sheet.