An X-ray CT apparatus can be configured such that an amount of artifacts of a tomographic image of a heart is reduced. For example, the X-ray CT apparatus can include detecting means for detecting a static cardiac time phase with a small amount of motion artifacts in a predetermined portion of the subject based on heartbeat information acquired in association with the projection data, and image reconstructing means for generating the tomographic image by reconstructing projection data corresponding to the static cardiac time phase detected by the detecting means.