In three dimensional X-ray imaging, a user interface is for search support with plural images, which are obtained by imaging an object upon applying X-rays thereto from an X-ray source. There is a display region for selecting two parallax images of one image pair among the plural images. Right and left buttons are for determining a direction to shift a view center of an image pair by selection from first and second directions in which an irradiation angle changes. A moving area image and line segment are for setting a small search area limited within an initial search area by considering the determined first or second direction, a first image pair specified previously, and a current second image pair in multi-stage binary search. Two parallax images of a third image pair are acquired from the small search area, to raise efficiency in search from the initial search area.
