A magnetron cathode assembly which realizes stopping of turn of an external terminal
inserted into a stem insulator without increasing a manufacturing cost. A leading
end of a base end axial portion of an external terminal has a non-circular section
by providing a flat surface in at least one position on its peripheral surface,
and a straight stop edge that fits to the flat surface thereby to carry out stopping
of turn of the external terminal is provided for a terminal fitting hole of a sealing
metal plate into which the leading end of this external terminal is fitted.