The present invention relates to an organic electroluminescent device comprising a substrate, a cathode, at least three organic material layers comprising a light-emitting layer, and an anode in the sequentially laminated form, in which the organic material layers comprise an n-type organic material layer positioned between the cathode and the light-emitting layer; and an organic material layer comprising a compound having a functional group selected from the group consisting of an imidazole group, an oxazole group and a thiazole group between the cathode and the light-emitting layer. The organic electroluminescent device according to the present invention comprises an organic material layer comprising a compound having a functional group selected from the group consisting of an imidazole group, an oxazole group and a thiazole group between a cathode and a light-emitting layer, thus having an improved electron injection characteristic to provide an organic electroluminescent device of an inverted structure operating at a low voltage.