An orientation degree distribution analysis method includes steps of: inputting, to a main storage device, crystal structure information of an object to be measured, information on an intensity ratio of each diffraction peak and a crystal plane corresponding to each diffraction peak by X-ray diffraction measurement, information on a diffraction range and a diffraction sensitivity, and information on an intensity ratio of each diffraction peak of a randomly oriented sample; calculating an angle defined by an orientation plane and a crystal plane corresponding to a diffraction peak of interest from the information stored in the main storage device; calculating an existence ratio and storing the existence ratio in the main storage device; setting an orientation degree distribution function; and calculating an orientation degree distribution from the information of the inputting step and the information of the calculating step.