An electron beam generating apparatus (1a) includes an electron gun (2), a vacuum container (3), a frame material (11), and a window material (13). The electron gun (2) has a filament (7) from which an electron beam (EB) is emitted. The vacuum container (3) holds the filament (7). The frame material (11) has an electron passing hole (11c) through which the electron beam (EB) passes, and is detachably attached to the vacuum container (3). The window material (13) is bonded (brazed) to the frame material (11) so as to airtightly stop up the electron passing hole (11c), and allows the electron beam (EB) to penetrate therethrough.