In an X-ray radiation source, a counter wall made of alkali-containing glass, out of walls of a housing of an X-ray tube, is sandwiched between a filament and an electric field control electrode to each of which a negative high voltage is applied. This configuration prevents an electric field from being generated in the counter wall and thus suppresses precipitation of alkali ions from the glass. Therefore, it prevents change in potential relationship between electrodes at different potentials such as the filament, grid, and target and enables stable operation to be maintained, without occurrence of a trouble of failure in maintaining a desired X-ray amount.