X-ray CT apparatus

An X-ray CT apparatus according to an embodiment includes a photon counting detector and processing circuitry. The photon counting detector includes a plurality of detection areas arranged in a channel direction and a column direction and is configured to output detection signals corresponding to the quantity of photons incident thereto, the detection areas each including a plurality of detecting elements. The processing circuitry is configured to calculate a heat generation amount for each of the detection areas on the basis of the detection signal corresponding to the incident photons detected in the detection area, to determine a control amount on the basis of the heat generation amount calculated for each of the detection areas, and to control temperature in each of the detection areas by using the determined control amount.