It is an object to provide a lightning arrester having machinery built-in in which an axial length of an insulating tube which stores therein zinc oxide elements is reduced so that an attempt is made for miniaturization. The arrangement is as follows. That is, a metal cap with an inclination portion 11 which is fixed to one end of the insulating tube 4 which stores therein the zinc oxide elements 5 is made to a dish shape which projects toward the anti-side of the zinc oxide elements, openings 11a are formed in the inclined portion thereof so that the inside and the outside of the insulating tube 4 communicate with each other, an insulating medium is circulated through the openings 11a while a sufficient gap L is formed between the one end of the insulating container 4 and a ground bracket 15, and the zinc oxide elements 5 are cooled by the insulating medium.