PURPOSE: To enable to increase a surface temperature of a heating part to a fixed level in a short period of time, by making an external diameter and a protected length of a heating part with a built-in heating wire made of a material having a high positive resistance temperature coefficient into the specific measurements.

CONSTITUTION: A heating part 10 is constituted by incorporating a heating wire made of a material (example, a material made up by adding rare earths to pure Ni) having a high positive resistance temperature coefficient into a metal protecting tube 2 through an insulating material 3. An external diameter D of the heating part 10 is made into less than 3.5mm, a reinforcement material 5 is installed on the circumference of the heating part 10 and an extrusion length L of the heating part 10 from the reinforcement material 5 is made into less than 6 times of the external diameter D. Rising of a temperature, consequently, of the heating part 10 through electrification is accelerated, through which an engine can be started instantaneously without preheating it even in a cold season and it enables engine to bear against severe coldness, heat and vibration in a practical state.