Small-sized X-ray CT apparatus obtaining a cross-section or 3D image of a sample, using X-rays. Included: an X-ray generating apparatus irradiating X-rays on the sample an X-ray detecting device detecting X-rays passing through the sample and a device processing a detection signal from the X-ray detecting device, to re-structure the cross-section or 3D image of the sample an X-ray shielding member having an opening portion for introducing the sample therein on one end surface and being treated with an X-ray protection process on an entire periphery thereof and a means rotationally driving the X-ray shielding member, wherein the X-ray generating apparatus and the X-ray detecting device are treated with the X-ray protection process, respectively, and are fixed on a wall surface of the X-ray shielding member at positions opposing to each other, putting an rotation axis thereof therebetween, and thereby constructed with the X-ray shielding member in one body.
