An X-ray computed tomography apparatus includes, an X-ray source which irradiates an object with X-rays spreading in a slice direction, an X-ray detector including a plurality of X-ray detection elements which are juxtaposed in the slice direction and detect X-rays transmitted through the object, a reconstruction unit which includes a back-projection unit which obtains back-projection data relating to each of a plurality of pixels defined in an imaging area by performing back projection of data acquired by the X-ray detector and an interpolation unit which interpolates the data, and performs reconstruction processing for an image, and a setting unit which sets central positions of a plurality of pixels in the imaging area in the reconstruction processing to positions offset from positions corresponding to centers of the X-ray detection elements in the slice direction.