A surface light source device includes a light source body, first and second electrodes, a light reflecting layer, and a fluorescent layer. The light source body is configured to generate light. The first and second electrodes are each disposed adjacent to a corresponding opposite end portion of the light source body. The first and second electrodes receive a discharge voltage that creates a potential difference across the light source body. The light reflecting layer is disposed at an internal surface of the light source body. The light reflecting layer includes light diffusing particles having at least two sizes. The fluorescent layer is disposed at selected regions of the light source body. Therefore, the light reflecting layer is not deformed by heat and enhances reflectivity without changing a color coordinates.