Provided is a method of fabricating an organic light emitting device that may form a light scattering layer having an irregular random structure at a low temperature. The method includes providing a substrate coated with a precursor layer; sequentially forming a metal layer and an organic layer on the precursor layer; performing a heat treatment of the organic layer to form an organic mask from the organic layer; patterning the metal layer by using the organic mask to form a metal mask; patterning the precursor layer by using the metal mask to form a light scattering layer having an irregular random structure; removing the metal mask and the organic mask; and sequentially stacking a planarization layer, a first electrode, an organic light emitting layer, a second electrode, and a passivation layer on the light scattering layer.