PURPOSE: To improve operability by making necessary and sufficient display by few monitors, and by securing a sufficient space near a table in an examination room without disturbing a catheter operation.

CONSTITUTION: This displaying method displays a reference image which is predetermined based on the kind of the specific image and whether it is a frontal image or a side image depending on the display of the frontal image or the side image of the predetermined specific image, adjacently to the specific image in pairs. For example, in the biplane radioscopic, the frontal (or the side) radioscopic image is displayed on the first monitor 66 as a specific image and the map image on the same side is displayed on the second monitor 67 as the reference image. In the case of the biplane images before and after PTA surgery, the image after surgery is displayed on the first monitor 66 as a specific image, and the image on the side before surgery is displayed on the second monitor 67 as the reference image.