To provide an alloy type thermal fuse which secures good operation property although spaces on both sides of a low-melting-point alloy piece are eliminated, and reduces a size sufficiently.

Wetting spread-preventing layers (s) with poor wettability with respect to wettability of surfaces of lead conductors are formed on surface parts of the lead conductors 1 adjacent to both ends of the low-melting-point alloy piece 2 respectively. Respective ends of the solidification low-melting-point alloy pieces 2 are terminated on tip ends of the wetting spread-preventing layers (s).