Included are a storage unit for storing as first medical image information a three-dimensional image representing information about an inside of the subject an image processor for generating a display image on the basis of the first medical image information and second medical image information and a display for displaying the display image generated by the image processor. The image processor includes: a catheter position information detector for calculating a position of the balloon catheter C and detecting position information and a balloon pressure-contact degree calculator for calculating a pressure-contact degree A of the tissues of the subject and a balloon b on the basis of the first medical image information and the position information.
