In order to suppress reduction in sensitivity when acquiring high-resolution data, an X-ray CT device is provided with an X-ray source that irradiates a patient with X-rays, and an X-ray detector that detects the X-rays. The X-ray detector includes a plurality of detection elements (scintillators and photodiodes) arrayed in a first direction, and a plurality of separators that separate the detection elements arrayed in the first direction respectively from each other. The separators each have a first-direction width which is a width in the first direction, first-direction widths of some separators each arrayed every predetermined number of separators being different from first-direction widths of the other separators.
