In friction areas, many complex phenomena occur which involve the formation of the hydrodynamic fluid film, direct contacts between sliding surfaces leading to wear and crack initiation, and adsorption and desorption and chemical reaction of additives contained in oil to the surfaces. In-situ observation has been conducted by using a transparent material as one side of the surfaces for a better understanding of complex phenomena occurring in the friction area. This paper introduces an in-situ synchrotron X-ray diffraction (XRD) observation system for the friction area that authors developed in recently. The developed XRD observation system succeeds in detecting simultaneously the XRD ring,visible image, and near infrared image of the friction area between a rotating sapphire ring and a steel pin at 30 times per second. Information obtained by the developed in-situ observation system appears to contribute to a better understanding of the dynamics of the surface occurring in the friction area.