1. An X-ray diagnosis apparatus comprising: an X-ray irradiation device configured to irradiate an object with an X-ray, the device including an X-ray source configured to generate an X-ray and a movable aperture device including multiple aperture blades configured to form an X-ray irradiation field; an X-ray detection device disposed to be opposed to the X-ray irradiation device and configured to detect the X-ray; a retainer configured to retain the X-ray irradiation device and the X-ray detection device; and processing circuitry configured to generate a last image hold (LIH) image as a static image by using a radiography irradiation field as the X-ray irradiation field, generate fluoroscopy images by using a fluoroscopy irradiation field as the X-ray irradiation field, the fluoroscopy irradiation field being narrower than the radiography irradiation field, generate superimposed images in which the fluoroscopy images are superimposed on a part of the LIH image, display the superimposed images on a display device, slides the aperture blades to enlarge or contact the fluoroscopy irradiation field of the fluoroscopy images, included in the corresponding superimposed images, with a fixed center of the fluoroscopy irradiation field, when an enlarging or contracting instruction of the fluoroscopy irradiation field is input, while the superimposed images are displayed, from an input device, and enlarge or contact the fluoroscopy irradiation field of the fluoroscopy images, included in the corresponding superimposed images, with the fixed center, when the enlarging or contacting instruction of the fluoroscopy irradiation field is input, while the superimposed images are displayed, from the input device, wherein an area which is inside a first fluoroscopy image before the contracting and which is outside a second fluoroscopy image after the contracting is applied, indicates a part of the LIH image.