X-ray diffraction method can be used for non-destructive stress measurements of crystalline materials. In this study, possibility of the X-ray stress measurements of implant materials placed in the body was investigated by using the skin and subcutaneous tissue covered Ti materials. Using the characteristic X-rays Mo-K
, diffracted X-rays from
-Ti could be detected transmit through the rabbit’s skin tissue of 1 mm thickness. The strains of (110) lattice planes of
-Ti specimen under bending deformation were obtained using parallel beam method. The strain components are estimated from the strains inclined to the nominal direction of the surface. The stress was calculated by using the relationship between the diffracted angle and the inclined angle (sin2
method). The stress of Ti implants could be estimated from the (110) lattice strain measured by X-ray diffraction method when the Ti implants were located under the skin tissue.