An X-ray CT apparatus of an embodiment includes a gantry and a control device held by the gantry. The control device includes processing circuitry. The processing circuitry is configured to collect data corresponding to energy of a material, adjust conditions for the data at the time of collecting the data, bundle the data distinguished in some of a plurality of energy bins, aggregate the collected data and the bundled data, and switch between the aggregation of the collected data and the aggregation of the bundled data.