A planar light source device comprises a light guide member having light scattering members for scattering light on the rear face of it, and a first LED module and a second LED module arranged on an end face of the light guide member. The light guide member has an area having no light scattering members in the vicinity of the LED modules, and has a corner-cut portion obtained by cutting a corner at an inclination angle in the light outputting direction of the first LED module. The first LED module is provided in the middle of the short side face of the light guide member, and the second LED module is provided on the corner-cut portion of the light guide member. The light from the first and second LED modules is outputted into an area where light scattering members are sparse.