An organic electroluminescent (EL) device (indium thin oxide/N,N’-diphenyl-N,N’-bis(3-methylphenyl)-(1,1’-biphenyl)-4,4’-diamine (TPD)/tris(8-hydroxyquinoline)aluminum (Alq(3))/Al) was prepared to observe the degradation process of the EL device by fluorescence microscopy and atomic force microscopy (AFM). From AFM and fluorescence microscopy observations, we found morphological changes of the Al top electrode surface, e.g. the formation of a dome in the form of a hemisphere. The surface morphology of the Al electrode changed with time, from tiny to growing disks with central sharp peaks, the dome formation, and finally formed crescent shapes due to shrink of the domes. However, under the crescent shape or the dome, there was little change in the organic layer except for the formation of a crevasse. The dome was formed by gas evolution from the crevasse.