A high-efficient phosphorescent cyclometalated transition metal complex represented by the formula M(C^N)( C^N)'(CN-R)X, and an organic electroluminescent (EL) device using the same. The transition metal complex can be used in formation of an organic layer of the organic EL device and produce white light emission when used together with a green-emitting material and a red-emitting material as well as emission at the wavelength range of 400-650 nm.