A protective device including a substrate, a conductive section and a first auxiliary medium is provided. The conductive section is supported by the substrate, wherein the conductive section comprises a metal element electrically connected between first and second electrodes. The metal element serves as a sacrificial structure having a melting point lower than that of the first and second electrodes. The first auxiliary medium is disposed between the metal element and the substrate, wherein the first auxiliary medium has a melting point lower than that of the metal element. The first auxiliary medium facilitates breaking of the metal element upon melting.