1. An X-ray CT (Computed Tomography) device comprising: a data collection section for imaging a subject with N different types of energy distributions so as to obtain the N types of projection data; and an imaging control section for converting the obtained N types of projection data into N+1 types of reference substance penetration distance data which are reconstructed to obtain reference substance equivalent tomographic images, wherein the imaging control section obtains the penetration distance data of a substance {A} contained in the N+1 types of reference substances by executing p-value conversion of an image G reconstructed using the N types of projection data for reprojection, determining a contribution of the substance {A} in the N types of projection data using the obtained penetration distance data for removing the contribution, and converting the projection data after removal into the penetration distance data for image reconstruction so as to obtain N+1 types of reference substance equivalent tomographic images M 1 .