To suppress the evaporation of easily gasifiable components of a seal 4 to lessen or reduce the white smoke production to substantially null even under a high applied load of a fuse resistor for operating a thermal fuse 3 with heat generated from an abnormally energized resistor 2, wherein series connection body A of the resistor 2 with the thermal fuse 3 is housed in a heat-resistive case 1 having an opening, lead conductors 21, 31 of the body A are led out of slits 12, 13 of the case 1, and the seal 4 is filled in the case 1 with mainly an inorganic powder and a heat-resistive effect resin used as a binder.

A heat transfer plate 5 contacts with the resistance element fuse 2 and extends over the thermal fuse 3 and is buried in the seal 4. This suppresses both the duration time of evaporation of water content of the seal and the evaporation quantity per unit time, thereby effectively preventing the white smoke from production.