The present invention relates to a thin organic electroluminescent device capable of preventing permeation of oxygen or moisture. The organic electroluminescent device according to one embodiment of the present invention includes a substrate, a plurality of pixels and a planarization layer. The substrate has grooves formed at the periphery of an active area. The pixels are formed in the active area. The planarization layer covers the pixels on the substrate. The passivation layer covers the planarization layer and the grooves. Since the organic electroluminescent device includes the grooves or path extending sections, oxygen (O2), water (H2O), etc. are not permeated into the inside of a passivation layer.