The invention provides an electron beam apparatus that reduces a time required for an electron gun chamber to which a sputter ion pump and a non-evaporable getter pump are connected to reach an extreme high vacuum state. The electron beam apparatus includes an electron gun configured to emit an electron beam and the electron gun chamber to which the sputter ion pump and the non-evaporable getter pump are connected. The electron beam apparatus further includes a gas supply unit configured to supply at least one of hydrogen, oxygen, carbon monoxide, and carbon dioxide to the electron gun chamber.