The present disclosure relates to an X-ray tube, and more particularly, to an X-ray tube having a simple structure from which an element necessary for focusing an electron beam, such as a magnetic lens, and having generating an X-ray having a focal spot of a nanometer-scale. The present disclosure includes: a electron beam generation unit emitting an electron beam; a limiting electrode unit limiting the electron beam emitted from the electron beam generation unit; and a target unit including a target material emitting an X-ray when the limited electron beam collides with the target material, wherein the limiting electrode includes of an electron beam limiting electrode allowing a portion of the emitted electron beam to pass therethrough and to be delivered to the target unit.