A surface light source device includes light source driving means for driving light sources on a light emission block basis, a light exit area being sectioned into two or more light emission blocks, light quantity detecting means for detecting light quantities on the basis of output light beams that are led out from the two or more light emission blocks, and drive control means for adjusting emission light quantities of the light sources corresponding to the respective light emission blocks on the basis of light quantities that are detected during lighting periods when only one of the light emission blocks is lit up that are subjected to light quantity detection by the light quantity detecting means.