An X-ray crystal orientation measuring apparatus and a method thereof, for enabling to measure distribution of crystal orientations upon a crystal having the sub-grain structure, lineage structure, other than the single domain, with using X-ray, comprises, an XY stage 20 for mounting a crystal S to be measured thereon and being movable in X-Y directions, an X-ray generating device 50 for irradiating X-ray at a predetermined angle upon a measuring surface of the crystal to be measured on the stage, a high-sensitive two-dimensional detector 60 for detecting the diffraction image of X-ray, which is irradiated from the X-ray generating device upon the measuring surface of the crystal to be measured, and a control PC, wherein the control PC calculates out a central position of the diffraction image detected, from the detected screen, so as to calculate out the crystal orientation upon the measuring surface of the crystal to be measured.