PURPOSE: To prevent deflection between a magnetron body and a filter case and facilitate automatic assembling thereof by integrally providing a protruded portion having a spherical part on the end of yoke.

CONSTITUTION: A cylindrical protruded portion 3b having the spherical surface 3b' at the end and the barrel vault type recessed portion 3b" at the rear surface is integrally provided on the yoke 3 corresponding to a plurality of through holes 8a formed on the bottom part of filter case 8. The height H of the protruded portion 3 is almost equal to the dimension of thickness T of the upper yoke 3 as the material plate to be processed and can easily be formed by the press molding method. Provision of protruded portion 3 having the height H almost equal to the thickness T and the spherical surface 3b' at the end point ensures easy engagement through the correcting function to the specified position.