The residual stress of electroplated Zn-Ni alloy was analyzed using a new X-ray diffraction technique developed by the authors. The distribution of residual stress in the thickness direction can be obtained non-destructively using the present method. The principles of the method are explained and measurement of the stress of electroplated Zn-Ni alloy is described. The thickness of the plating examined was between 2 and 10 mu m. Non-linear sin(2) phi diagrams were obtained from all specimens, which suggested the existence of a steep stress gradient in the thickness direction. Microscope observation of cross-sections showed that there were cracks in the plating at areas where tensile stresses occurred.