According to one embodiment, An X-ray CT apparatus includes acquisition unit, intermediate image generating unit, weighting factor calculating unit, and resultant image generating unit. The intermediate image generating unit generates a first image based on a first projection data set and a second image based on a second projection data set. The first projection data set falls within a first view angle range of projection data acquired by the acquisition unit. The second projection data set falls within a second view angle range of the projection data. The second view angle range is narrower than the first view angle range. The weighting factor calculating unit calculates a weighting factor corresponding to a pixel value difference between the first image and the second image. The resultant image generating unit generates a resultant image associated with weighted addition of the first image and the second image based on the weighting factor.