In view of the effects of the hardness of material on fatigue, rolling contact fatigue process in hard metals seems to differ from it in soft metals. This paper has been aimed to compare the rolling contact fatigue process according to the hardness of materials. Rolling contact fatigue tests using the ball bearings assembled with the inner race of four different hardness have been carried out. In addition, residual stress and half-value breadth on/below the inner raceway during individual rolling contact fatigue have been measured by X-ray diffraction. The results of this study showed that the change of residual stress and half-value breadth during the rolling contact fatigue on race way in hard metals is the same as in soft metals. However, plastic deformation by rolling contact in hard metals is in microscopic scale but only for soft metals in macroscopic scale.