Abstract: Action on the tested wafer 1 is rendered with X-ray beam 3 converging in a point located inside the wafer or under it. Determination of relative position of the interference maxima is 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. Means 11 for beam shaping creates beam 3 simultaneously acting on multiple crystallographic planes. Detectors 13 receive diffracted radiation in the whole angular range containing the interference maxima corresponding to the reflections from the irradiated planes.