An anticathode is repeatedly moved along a rotating axis of the anticathode while the anticathode is rotated around the rotating axis. Then, energy beams are irradiated onto a surface portion of the anticathode which is located against a centrifugal force generated from the rotation of the anticathode to partially melt the surface portion through the heating said surface portion near the melting point of the anticathode or over the melting point of the anticathode, thereby generating an X-ray from the rotating anticathode.