The invention provides a thermal fuse and a fuse element of the low-melting fusible alloy type. The fuse element has an alloy composition in which a total of 0.01 to 7 weight parts of at least one selected from the group consisting of Au, Bi, Cu, Ni, and Pd is added to 100 weight parts of a composition of 100% In, that of 90 to 99.9% In and 0.1 to 10% Ag, or that of 95 to 99.9% In and 0.1 to 5% Sb. As a result, the operating temperature is in the range of 135 to 160.degree. C., requests for environment conservation can be satisfied, the diameter of the fuse element can be made very thin or reduced to about 300 .mu.m.phi., and the thermal stability can be satisfactorily guaranteed.