Abstract: Disclosure is made of a cathode assembly of an electron beam welding gun, wherein in a holder's sleeve, which is mounted an a current lead, there is arranged a disc cathode. Arranged in the cavity of said current lead, coaxially therewith, are two more current leads. The latter two current leads are concentric to each other; in said current leads there is secured a flat coil with a central end bent at a perpendicular to the coil's plane. Said central end, bent at a perpendicular to the coil's plane, is corrugated along its axis and installed in a current lead constructed as a rod having a stepped cavity extending along the rod's axis. The outer turn of said coil is arranged in another current lead which envelops the above-mentioned current lead and is constructed as a tube with an internal annular recess at its end, which receives the outer turn of said coil.