1. An X-ray diagnosis apparatus, comprising: an image data generating unit configured to generate X-ray images in a time sequence by detecting, with a detector, an X-ray that is radiated from an X-ray tube and is transmitted through a subject; a processor configured to detect a position of an X-ray impermeable feature point included in a treatment equipment for an interventional treatment from at least a first image and a second image included in the X-ray images generated in a time sequence by the image data generating unit, determine an application range of a smoothing filter in the first image and the second image based on the detected position of the feature point in the first image and the detected position of the feature point in the second image, and perform a smoothing filter process by using the first image and the second image based on the determined application range of the smoothing filter.