To provide a surface light source device which eliminates a gap between a light guide plate and a frame and generation of interference fringes of light and the like and is small-sized and lightweight.

The surface light source device 7 is provided with the surface-like light guide plate 20 and the frame 2 for holding at least the light guide plate 20 formed abutting on side surfaces except the side surface on the light incidence side and having a reflection function and the frame 2 and the light guide plate 20 are integrally formed. Light from a white LED 3 inserted in a recessed part 22 of the frame 2 is made incident from a light incidence surface of the light guide plate 20 and emitted from a light emission surface of the surface-like light guide plate 20.