A photon counting CT device of an embodiment comprises an X-ray tube, a scintillator, an avalanche photodiode array, a holding part, a dividing part, and an image generation part. The X-ray tube generates X-rays. The scintillator converts the X-rays generated by the X-ray tube into light. The avalanche photodiode array is composed of a first pixel which is in a first range which is a light receiving range of the scintillator's light and which comprises an avalanche photodiode that outputs an electrical signal on the basis of the light, and a second pixel which comprises an avalanche photodiode that is in a second range which has a different location from the first range. The dividing part counts the number of photons of the light that enters the first pixel by dividing an integrated value of the electrical signals output by the first pixel by the value of the electrical signals held by the holding part. The image generation part reconstructs an image on the basis of the counted number of photons of the light.
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