In a surface light source device (1), a positive reflective region (23) of a reflective member (20) that is disposed on the bottom surface (4) of a housing (2) reflects light output by a light emitting device (14) toward a direction away from the light emitting device (14). As a result, the brightness of the light in the proximity of the light emitting device (14) of the surface shaped illuminating light output by a light emitting surface member (3) can be suppressed, and the brightness of light of a central part (position furthest away from the light emitting device (14)) of the surface shaped illuminating light output by the light emitting surface member (3) can be increased.