An X-ray imaging machine is configured such that a three-dimensional blood-vessel information creating unit creates information concerning a three-dimensional blood-vessel core line and a position of a plaque in a subject blood vessel based on three-dimensional volume data obtained from an image taken by an X-ray computed tomography apparatus. A plaque-depth information image creating unit creates a plaque-depth information image on which the plaque is differently displayed in accordance with whether the plaque is present in front of or in the back of the three-dimensional blood-vessel core line with respect to a projection direction, based on the created information concerning the three-dimensional blood-vessel core line and the position of the plaque. An X-ray image display unit displays the created plaque-depth information image over an X-ray image in a superimposed manner.
