Provided are an organic electroluminescent device and a method of manufacturing the same. An organic electroluminescent device, comprising a rear substrate, an organic electroluminescent unit formed on one surface of the rear substrate and having a first electrode, an organic film, and a second electrode, and a front substrate joined to the rear substrate and having a porous oxide layer based on alumina on an inner surface of the front substrate. The alumina is hydrated amorphous alumina. The porous oxide layer is composed of hydrated amorphous alumina; hydrated amorphous alumina and silica; hydrated amorphous alumina, and one or more selected from alkaline metal oxide, alkaline earth metal oxide, metal halide, metal sulfate, and metal perchlorate, which are captured in a network of the alumina; or hydrated amorphous alumina, silica, and one or more selected from alkaline metal oxide, alkaline earth metal oxide, metal halide, metal sulfate, and metal perchlorate, which are captured in a network of the alumina and a network of the silica. The organic electroluminescent device may be used as a front emission type, a rear emission type, or a both-direction emission type display.