PURPOSE: To accomplish a high current density cathode of impregnation type which operates at low temp. and is equipped with long life, by furnishing the cathode over its surface with a hybrid thin film island-shapedly being made of W and oxides including W and Sc.

CONSTITUTION: An impregnation type cathode concerned comprises a heat resistant porous base 1, an electron emitting substance 2 chiefly containing Ba having permeated small holes in this base 1, and a hybrid thin film of including at least W and oxides of W and Sc provided over the surface of the base, wherein the hybrid thin film shall be embodied in the form of an island. That is, a proper amount of Ba is supplied to the cathode surface even though the total amount of Ba supply from substratum cathode pellets 3 decreases, by means of performing Ba supply not only with dispersion through the thin film but also with facial dispersion. This accomplishes a low temp. operating type cathode equipped with a long life, in which the high density of the emission current can be maintained for a long time.