A X-ray generating device includes a chamber, a rotating body in the chamber, a starting material storage vessel for storing a target starting material in liquid form, and a starting material supply mechanism for applying the target starting material onto a surface of the rotating body. The X-ray generating device also includes an energy beam inlet window disposed at an opening of the chamber and configured to transmit an energy beam, which will be directed onto the target starting material on the surface of the rotating body and introduce the energy beam from the exterior of the chamber to the interior of the chamber, and an X-ray outlet window disposed at the opening of the chamber and configured to transmit the X-rays, which are generated upon irradiating the target starting material with the energy beam, and allow the X-rays to proceed to the exterior of the chamber.