To provide a surface light source which has a good light utilizing efficiency and is adapted for high luminance and low power consumption.

A first and a second light diffusion sheets 6, 8 are supported vertically at a prescribed distance by a frame body 5 above a substrate 3 on which are disposed a plurality of blue color type LEDs 4, and one of the light diffusion sheets, 6, integrally provided with a fluorescent material which emits fluorescence according to light of the LED 4. The frame body 5 is constructed by combining an upper and a lower frames 53, 54, and the light diffusion sheet 8 is held between the upper and the lower frames 53, 54.