1. An X-ray diagnosis apparatus comprising: image generating circuitry configured to repeatedly generate X-ray images on the basis of X-rays radiated from an X-ray tube and passed through a subject; feature point detecting circuitry configured to detect, each time one of the X-ray images is generated, a position of a feature point of a stent retained in the subject on each of the X-ray images; correction-image generating circuitry configured to generate, each time the position of the feature point is detected, a correction image by performing correction processing for substantially matching up the position of the feature point detected on a first X-ray image and the position of the feature point detected on a second X-ray image that is an X-ray image generated after the first X-ray image, the correction processing being performed on the second X-ray image; addition-correction-image generating circuitry configured to generate, each time when the correction image is generated, an addition correction image obtained by adding together the correction image and at least one correction image generated before the correction image; display control circuitry configured to perform control of displaying a moving image of the X-ray images and to perform control of displaying a moving image on which the stent is almost stationary being obtained by performing control of displaying, each time when the addition correction image is generated, a newly generated addition correction image as an image for display; and a display being controlled by the display control circuitry and configured to display the moving image of the X-ray images and the moving image on which the stent is almost stationary, wherein the feature point detecting circuitry starts to detect the feature point when a stent-fixation-function is turned on by an operator.