An alloy type thermal fuse is provided in which a ternary Sn—In—Bi alloy is used, the operating temperature belongs to the range of 130 to 170 C., the overload characteristic and the dielectric breakdown characteristic are excellent, the insulation stability after an operation can be sufficiently ensured, and thinning of a fuse element can be easily realized. A fuse element having an alloy composition in which Sn is larger than 43% and 70% or smaller, In is 0.5% or higher and 10% or lower, and a balance is Bi is used.