An organic electroluminescent device and its method of manufacturing are provided. The organic electroluminescent device may include a rear substrate, an organic electroluminescent unit including a first electrode, an organic film, and a second electrode stacked on a surface of the rear substrate. It may also include a front substrate joined to the rear substrate to seal an internal space in which the organic electroluminescent unit is disposed. It may also include a porous oxide layer composed of a porous silica and a metal compound on a lower surface thereof. A device constructed according to the present invention may have excellent adsorption of moisture and oxygen, thereby increasing the life span of the device.