An organic light emitting device, and a method of fabricating the same, has a
cathode electrode that can prevent oxygen or moisture from infiltrating. The organic
light emitting device of the present invention has a lower electrode, an organic
thin film layer and an upper electrode successively formed on the substrate. The
upper electrode has at least two-layered thin films having different grain density
and grain size. A lower film of the at least two-layered thin films of the upper
electrode has a first Al thin film having a lower grain density and larger grain
size than an upper of the at least two-layered thin films. The upper film has a
second Al thin film having relatively higher grain density and smaller grain size
than the first Al thin film.