PURPOSE: To obtain an electrode filament with high efficiency by depositing and forming an LaB6 coating layer for a thermion emission material on a matrix metal wire using the discharge coating. method.

CONSTITUTION: A surface coating layer 2 made of LaB6 is formed on the surface of a tungusten wire 1 at a thickness below 10 microns using the discharge coating method. The discharge coating uses a method in which while a coating material electrode and a metal wire are being made to touch, separated, oscillated or rotated and slided, discharge is generated between both and the coating material is deposited to a matrix metal wire, a method in which a coating material wire is dissolved and scattered by shock discharge and is made to collide against the matrix metal wire, a method in which coating material powder is jetted by shock discharge and is made to collide against the matrix and is deposited and applied, a method in which shock discharge is performed between the coating material electrodes opposed to the matrix, and such. As a result, the coating layer can be formed on the surface of the matrix metal wire as the LaB6 compound without decomposing the coating material LaB6 and the coating layer that is deposited to the matrix and is coupled tightly can be obtained.