In order to reduce a metal artifact using a short process, without causing image quality deterioration, when a subject containing metal is imaged in an X-ray CT apparatus, the invention is such that a high frequency component is extracted utilizing the fact that a high frequency component is a structure in error projection data, which are a difference between primary corrected projection data wherein at least one portion of an artifact component caused by metal has been removed and photographed projection data acquired by imaging. The high frequency component, extracted while carrying out weighting in order to suppress the metal artifact, is restored to the primary corrected projection data, after which an image is reconstructed. Also, metal projection data used when compiling the primary corrected projection data are calculated from a value that is a CT value corresponding to soft tissue subtracted from a CT value of a metal region.
