PURPOSE: To heighten the bonding intensity of films protecting an element from water content, etc., by a method wherein the protecting films are formed of reaction assistant layers ' at least partly diffused on an element surface and $ protecting layers provided on the surface of the reaction assistant layers.

CONSTITUTION: Protecting films 4 are bond-formed on both upper and lower surfaces of a varistor element 1 as well ason the surface of an upper layer 3b in contact therewith. On the other hand, a lower layers 3a are reaction assistant layers least a part thereof diffused on the surface of the varistor element 1 and the upper layer 3b containing at least either one element out of Bi, Sb. Besides, the upper layers 3b filling the role of the protective layers contain at least one element out of Bi, Ti, Al while a part of the reaction assistant layers is diffused on the lower surface thereof. Accordingly, the outer surface of the varistor element 1 is covered with the protective films 4 and outer electrodes 3 furthermore, in the abutting parts thereof, a part of the reaction assistant layers is diffused in the outer electrodes 3 so that the bonding intensity of the protecting films 4 onto the element 1 may be so high thereby enabling the degeneration of the element 1 due to any water content, etc. to be avoided.