A photon counting computed tomography (CT) apparatus according to an embodiment includes a photon counting detector and processing circuitry. The photon counting detector detects X-ray photons to acquire energy information. The processing circuitry acquires at least one piece of information out of information on an imaging mode, information on a site to be imaged, and information on a medical device. The processing circuitry, based on the acquired information, determines at least one condition out of a condition on an energy band of data collected by the photon counting detector and a condition on an energy band for data for use in reconstruction processing out of the data collected by the photon counting detector.