An organic electroluminescent device and a conductive substrate thereof are provided. Said conductive substrate includes a glass substrate, an indium tin oxide (ITO) layer and a metal oxide layer located between said glass substrate and said ITO layer. The refractive index of said metal oxide layer ranges between that of said glass substrate and said ITO layer. Due to the metal oxide layer, the refractive index of which ranges between that of the glass substrate and the ITO layer, is inserted into said conductive substrate, when the light extracts between the ITO/metal oxide layer and the metal oxide layer/glass, the critical angle of total reflection increases compared with that without the inserted metal oxide layer. Most part of light extracts out of the interface after refraction, and only small part of light is totally reflected, thus the light extraction enhances.