A cyclometalated transition metal complex exhibiting phosphorescence with high efficiency and an organic electroluminescent display device using the same are provided. This transition metal complex can be used in forming an organic film of an organic electroluminescent display device. The transition metal complex can emit light at the wavelength range of 400 to 650 nm. Further, the complex can emit white light by using a green light emitting material or a red light emitting material together.