A method of discriminating left or right for breast regions, including generating data of plural breast images when a left breast region and a right breast region are alternately imaged in an order and are repeatedly imaged in various imaging directions in the same order by image generating sections arranged in a certain direction. A breast image is specified which is capable of being discriminated whether the imaged breast region is left or right among the plural breast images, and it is discriminated whether the left breast region or the right breast region is imaged concerning other breast images, based on the specified breast image and the order of imaging of the plural breast images of a single patient.
