An X-ray CT device of an embodiment includes processing circuitry. The processing circuitry acquires data corresponding to energy when X-rays radiated by an X-ray tube are transmitted through a subject. The processing circuitry adjusts conditions including first and second conditions for the data when the data is acquired. The processing circuitry switches the condition from the first condition to the second condition when an injection state of a contrast agent injected into the subject satisfies a predetermined condition. The processing circuitry bundles the data discriminated into some of a plurality of energy bins.