To provide an apparatus for coating partially a high quantum efficiency substance on a tip of a cathode, by which a photocathode type electron ray source having both the markedly high luminance and coherence and enabling an electron microscope such as a TEM, an accelerator, and an X-ray generation apparatus to have outstandingly improved performances in case that they use the photocathode type electron ray source, is realized.

The apparatus for coating partially of the present invention is used for coating the high quantum efficiency substance on the tip (15) of the cathode of the photocathode type electron ray source. The apparatus for coating partially is characterized in that a stop with an aperture for restricting a coating region on the tip (15) of the cathode is arranged between the tip (15) of the cathode and discharging sources (41 and 42) from which the composing substance of a high quantum efficiency substance coat is discharged.