Abstract: The inventions are directed to increasing of control reliability and providing of express test, thus creating possibility of total control of single-crystal wafers at different stages of manufacturing process. The method is based on the wafer tested being acted upon with X-ray beam, registration of interference pattern of diffraction and determination of relative position of interference maxima used to judge the presence of elastic strains. Method's feature lies in the wafer 1 being acted upon with X-ray radiation beam 3 converging in a point located inside the wafer at below it, and in determination of relative position of the interference maxima being performed for diffraction reflections from crystallographic planes having the form of nKK, where n is equal to H, K or L and differs for distinct crystallographic planes.