A planar light emitting device has a planar light emitter. It has a layered structure composed of a transparent body and a semi-transparent body. The transparent body is made of a transparent synthetic resin containing no light scattering material. The semi-transparent body is made of a semi-transparent synthetic resin containing a light scattering material. The transparent body and the semi-transparent body are joined to form a diffusion layer therebetween. An LED array is disposed at one side of the planar light emitter. The diffusion layer has a sea-islands structure. An island resin has a dimension of 0.1 to 50 microns. The light entering the island resin attenuates therein without reflecting at once due to its complicated shape. Namely, the light entering the diffusion layer generates uniform brightness.