According to one embodiment, an X-ray computed tomography apparatus includes an X-ray tube, X-ray detector, acquisition unit, rotating mechanism, input unit, and control unit. The input unit repeatedly inputs trigger signals originating from a specific phase of a periodic motion of a body of a subject or a periodic motion of an organ of the subject. The trigger signals being supplied from a measuring device which measures the periodic motion. The control unit causes the X-ray tube to start generating X-rays on the basis of the input of a first trigger signal of the repeatedly input trigger signals, and causes the X-ray tube to stop generating X-rays on the basis of the input of a second trigger signal next to the first trigger signal in order to repeatedly scan the subject over substantially one period of the movement while a scan position is fixed.