To provide a lead-free fusible alloy type thermal fuse having Sn-Bi based alloy as the main composition for temperature sensing element and 130-135°C acting temperature.

The low melting point fusible alloy 3 contained by adding or partially replacing 1 wt.% Ag and In or Ga into a binary alloy of 42Sn-58Bi as the base body alloy composition, is joined with a resistance welding with one pair of lead members 1, 2 composed of Sn-Cu plated copper wire. Flux 4 composed of rosin, wax and activators, is coated on the surface of the low melting point fusible alloy 3, and thereafter, this is held into an insulating case 5 of a ceramic porcelain tube, such as alumina, and constituted by sealing both end parts of the insulating case 5 while remaining the delivering parts of the lead member 1, 2 with heat resistant sealing members 6, 7 of epoxy resin and inorganic additive.