To satisfactorily control variation in a working temperature of a thermal fuse using a fuse element made from an In-Sn-Bi ternary alloy, or an alloy further containing Ag and Cu on the basis of the ternary alloy, to control the working temperature of the thermal fuse to around 100°C or lower, and to fully secure the low resistance and the mechanical strengths of the fuse element.

The thermal fuse employs a low-melting fusible alloy for the fuse element 1, wherein the low-melting fusible alloy has an alloy composition comprising 50-55% In, 25-40% Sn and the balance Bi. The alloy preferably further comprises 51-53% In, 32-36% Sn and the balance Bi.