An ESD protection device comprising: a ceramic base material including a glass component; opposed electrodes including an opposed electrode on one side and an opposed electrode on the other side, the opposed electrodes formed so as to have their ends opposed to each other at a distance therebetween in the ceramic base material; a discharge auxiliary electrode connected to a first principal surface of each of the opposed electrode on one side and the opposed electrode on the other side constituting the opposed electrodes, the discharge auxiliary electrode placed so as to provide a bridge from the opposed electrode on one side to the opposed electrode on the other side, wherein the discharge auxiliary electrode includes metallic particles and a ceramic component, the ceramic component interposed between the metallic particles; a discharge gap section where the opposed electrode on one side and the opposed electrode on the other side for constituting the opposed electrodes are opposed to each other, the discharge auxiliary electrode not filling the discharge gap section; a cavity section provided in the ceramic base material at a second principal surface of the opposed electrodes, the cavity section including the discharge gap section; and a sealing layer, characterized in that the sealing layer is formed between the discharge auxiliary electrode and the ceramic base material, and between at least a part of the first principal surface of the opposed electrodes and the ceramic base material, and the sealing layer is a porous layer which functions to absorb and trap a glass component of the ceramic base material and a glass component produced in the ceramic base material in a firing step, thereby preventing the ingress of the glass component from the ceramic base material into the discharge auxiliary electrode. a ceramic base material including a glass component; opposed electrodes including an opposed electrode on one side and an opposed electrode on the other side, the opposed electrodes formed so as to have their ends opposed to each other at a distance therebetween in the ceramic base material; a discharge auxiliary electrode connected to a first principal surface of each of the opposed electrode on one side and the opposed electrode on the other side constituting the opposed electrodes, the discharge auxiliary electrode placed so as to provide a bridge from the opposed electrode on one side to the opposed electrode on the other side, wherein the discharge auxiliary electrode includes metallic particles and a ceramic component, the ceramic component interposed between the metallic particles; a discharge gap section where the opposed electrode on one side and the opposed electrode on the other side for constituting the opposed electrodes are opposed to each other, the discharge auxiliary electrode not filling the discharge gap section; a cavity section provided in the ceramic base material at a second principal surface of the opposed electrodes, the cavity section including the discharge gap section; and a sealing layer, characterized in that the sealing layer is formed between the discharge auxiliary electrode and the ceramic base material, and between at least a part of the first principal surface of the opposed electrodes and the ceramic base material, and the sealing layer is a porous layer which functions to absorb and trap a glass component of the ceramic base material and a glass component produced in the ceramic base material in a firing step, thereby preventing the ingress of the glass component from the ceramic base material into the discharge auxiliary electrode.