The present invention provides a planar lighting device that responds to the need for lightness and thinness and has excellent brightness characteristics. A planar lighting device according to an embodiment includes a light guide plate that emits light incident from a side surface of the light guide plate from an emission surface of the light guide plate; a light source that is disposed on the side surface side and has a light-emitting surface generating light incident to the side surface; a substrate having two main surfaces, the surface on the opposite side of the light-emitting surface of the light source being installed on one main surface; a frame having a side surface and a bottom surface and accommodating the light guide plate, and the light source and the substrate; a first connection member disposed between the light guide plate and the bottom surface and between the light source and the bottom surface and connecting the light guide plate and the light source.