According to one embodiment, an X-ray computed tomography apparatus includes processing circuitry. The processing circuitry sets a parameter of an examination protocol. Based on the set parameter, the processing circuitry determines the number of acquisition views and the number of reconstruction views of projection data. The processing circuitry acquires first projection data corresponding to the number of acquisition views. The processing circuitry calculates second projection data corresponding to the number of reconstruction views based on the first projection data. The processing circuitry reconstructs a CT image based on the second projection data.