PROBLEM TO BE SOLVED: To provide an X-ray CT apparatus and a method for upsampling projection data capable of acquiring upsampled projection data closer to the measured values.SOLUTION: An X-ray CT apparatus 1 acquires the projection data for one rotation (2&pgr rotation) and uses opposite data, in which the X-ray transmission path in the acquired projection data is substantially coincide, to perform upsampling, for example, in a view direction. That is, a virtual channel is inserted between each channel in a real view, the value of the virtual channel is determined by interpolation calculation or the like, and the determined value of the virtual channel is added to the corresponding point at the virtual view position of the opposite data in which the X-ray transmission path is substantially coincide. This process is repeated to generate a virtual view between real views. The data of each channel in the virtual view is determined by interpolation calculation or the like using the value of each corresponding point in the virtual view.
