In an X-ray CT apparatus 1 and an X-ray CT method, the thickness of an object to be inspected is computed on the basis of the number of transmitted X-rays in a specific energy range set above and below the K-absorption edge of an X-ray contrast medium serving as the object to be inspected, and a CT image is reconstructed on the basis of the computed thickness of the object to be inspected. Such X-ray CT apparatus 1 and X-ray CT method can generate an X-ray CT image stably and independently of the size of the object to be inspected and of X-ray tube voltage (X-ray energy distribution).