Provided is an electrostatic discharge (ESD) protection device that has good initial insulation properties and a good operation ratio at relatively low discharge voltages. The ESD protection device comprises: an insulating substrate; discharge electrodes that are first and second discharge electrodes disposed so as to be in contact with the insulating substrate and so as to oppose one another at a distance; external electrodes that are first and second external electrodes disposed on the outer surface of the insulating substrate and electrically connected to the first and second discharge electrodes, respectively; and a discharge auxiliary electrode that straddles the first discharge electrode and the second discharge electrode in the region in which the first and second discharge electrodes oppose one another. The discharge auxiliary electrode comprises semiconductor particles and metal particles with a mean particle diameter of 0.3-1.5 mum and the density of presence of the metal particles in an arbitrary cross-section of the discharge auxiliary electrode is at least 20 particles per 50 mum2.