An image processor and X-ray diagnostic apparatus designate areas of interest, by using an input unit, on at least two of a plurality of still images forming a moving image when continuously displayed, estimate corresponding areas on the remaining images which correspond to the areas of interest by geometrical calculation or the like by using a position detecting section, shift the respective areas of interest and the respective corresponding areas to the image centers of the respective images by using an AFFINE transformation section, and perform continuous display by using the respective images after the shift processing.