According to one embodiment, an X-ray computed tomography apparatus includes an X-ray tube, a detector, and processing circuitry. The X-ray tube emits X-rays. The detector detects X-rays that have been emitted from the X-ray tube and have passed through the subject. The processing circuitry sets an imaging condition. The processing circuitry evaluates the imaging condition based on information on a lower limit range of a count value of the detected X-rays that may cause image degradation.
