A surface light source device includes a plurality of LEDs for emitting a plurality of light having different colors, and a light guide body for mixing the colors of the plurality of light and emitting light having colors mixed. The light guide body includes a light incident portion for causing the plurality of light to be individually incident, and a light emitting portion provided beside the light incident portion and changing propagation angles of the plurality of light which is incident from the light incident portion and propagated into the light guide body to mix colors, thereby controlling a quantity of light emission from the light guide body and a light emitting position.