An X-ray CT device which restricts a wasteful X-ray exposure to an object to be examined and applies a proper X-ray dosage, and which comprises an X-ray source, a detector, a scanner mounting them thereon, a high-voltage generating device, a control device, an image processing device and a display unit, wherein the X-ray CT device further comprises an operation means for setting the device's scanning condition, a scanogram analysis means for analyzing the scanogram image data of an object to be examined and generating the 3-D transmission length model of the object to be examined, an X-ray tube current setting means for automatically setting the variation pattern of an X-ray tube current according to the shooting location of the object to be examined based on the transmission length model of the object to be examined and a scanning condition, and a dosage calculating means for calculating a dosage applied to the object to be examined and displaying the calculation results on a display unit. <；IMAGE>；
