IVR-CT apparatus has an angio-image obtaining unit, an angio-image imaging direction obtaining unit, a CT-image obtaining unit, a blood vessel part extracting unit, a projected image generating unit and a display control unit. The angio-image obtaining unit obtains a required angio-image from multiple chronological angio-images. The angio-image imaging direction obtaining unit obtains a direction of imaging as incidental information included in data on the required angio-image. The CT-image obtaining unit obtains a three-dimensional CT-image corresponding to the required angio-image. The blood vessel part extracting unit extracts a blood vessel part in the three-dimensional CT-image. The projected image generating unit generates a three-dimensional projected image by projecting the blood vessel part, and a three-dimensional projected image corresponding to a direction of a projection after a manual operation operates the direction of the projection. The display control unit makes display the three-dimensional projection image and the angio-image one over another.