An ESD protection device providing highly reliable insulation and having good discharge characteristics is provided. An ESD protection device has opposing first and second discharge electrodes, an auxiliary discharge electrode (18) astride between the first and second discharge electrodes, and an insulating substrate (12) supporting the first and second discharge electrodes and the auxiliary discharge electrode (18). The auxiliary discharge electrode (18) is composed of an assembly of core-shell metal particles (24) that have a core portion (22) mainly composed of a first metal and a shell portion (23) mainly composed of a metal oxide that contains a second metal. The metal particles (24) are substantially completely covered with the shell portion (23) mainly composed of the metal oxide, and this improves the insulation reliability of the device against discharge. Preferably, the metal particles (24) have a bond with each other with a vitreous substance (27) therebetween.