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 arranged opposite to a high-voltage region VH of a power supply unit including a high-voltage generation module which generates a negative high voltage to be applied to a filament. 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 prevents occurrence of a trouble of failure in maintaining a desired X-ray amount, thus enabling stable operation to be maintained.