According to an embodiment, X-ray CT apparatus includes X-ray generator includes X-ray tube, high-voltage generator, detector, controller and circuitry. High-voltage generator generates tube voltage to be applied to X-ray tube. Detector detects X-rays irradiated from X-ray tube and transmitted through a subject. Controller controls high-voltage generator to scan the subject with first radiation dose and with second radiation dose lower than first radiation dose. Circuitry generates first image based on projection data acquired by scan at first radiation dose, generates second image based on projection data acquired by scan at second radiation dose, and displays first image and second image in common window.
