To provide a resistance built-in thermal fuse with an electric conduction exothermic element and a temperature sensing fusing element on an insulation chip, in which a mounting work is made easy by making linear and planar a wiring arrangement of a lead member.

An insulative hexahedron chip 12 is provided with a thick resistance of an electric conduction exothermic element 20, a fusible alloy of a temperature sensing fusing element 30 and pattern electrodes 14, 16, 18 having both sides. These pattern electrodes are provided with main lead-out leads 24, 26 making an operation circuit and sub-lead-out leads 28 making a controlling circuit, and these lead members are formed in linear and planar wiring arrangement. Furthermore, these lead members are made of a planar conductor formed bent, and lead-out parts are formed straight on one face so that a mounting work and soldering work to a mounting circuit can be facilitated.