An X-ray CT device including a stationary part; a rotary part rotatable relative to the stationary part; an X-ray tube provided at the rotary part for radiating X-ray beams on an object; an X-ray detector provided at the rotary part opposing the X-ray tube, and that detects the X-ray beams passed through the object; an image processor that generates cross-sectional images of the object based on a detection signal outputted from the X-ray detector; a display that shows the cross-sectional images based on output signals delivered from the image processor; a first transmitting section configured by a rotary step-up transformer having a primary and secondary windings residing at the stationary and the rotary part respectively, and that steps up AC voltage provided by AC power source, and that further executes non-contact power transmission from the stationary part to the rotary part for supplying power to the X-ray tube.