At least one of center and ground electrodes of a spark plug has a thin layer formed by bonding noble metal powder on a discharge-related surface area of the electrode stock of said at least one of said center and ground electrodes in accordance with ultrasonic bonding. Instead of the thin layer, a discharge tip may be formed there by boring a hole in the electrode stock, filling noble metal powder, which has been obtained by coating spherical or flaky metal particles with a corresponding noble metal or noble metal alloy, in the hole and then bonding the thus-filled noble metal powder in accordance with ultrasonic bonding. As a further alternative, a tip made of a noble metal or an alloy thereof may be bonded by ultrasonic bonding or resistance welding in the hole with a layer or metal powder of a metal having good high-temperature erosion resistance or an alloy thereof interposed therebetween. The spark plug enjoys a long operating life.