The objective of the present application is to suppress the occurrence of flares and to reduce the amount of secondary electrons arising at an aperture provided to the lead-out electrode of an electron gun. By coating a thin film having a low rate of secondary electron emission such as carbon onto the aperture of a lead-out electrode closest to an electron source in an electron gun, it is possible to reduce the amount of secondary electrons arising. Secondary electrons arising at the lead-out electrode, are reduced, and so as a result, flare is reduced. By incorporating two apertures to the lead-out electrode, and applying to the two apertures a potential that is equipotential to the lead-out electrode, it is possible to eliminate an electric field from seeping from under to over the lead-out electrode. Secondary electrons arising when an electron beam impacts the lead-out electrode cease to incur force in the direction of passage from the lead-out electrode, and consequently there is a reduction in flares.