PURPOSE: To enable to start a diesel engine with ease in a cold district in winter, by lowering the combustion temperature of fuel by applying an oxidizing catalyst over the surface of the heating part of a glow plug.

CONSTITUTION: In case that a glow plug 4 is made of a ceramic material, the surface of the glow plug is impregnated with an oxidizing catalyst. In case that the glow plug 4 is made of a metal, on the other hand, a catalyst solution obtained by esterifying propylene glycol in a mixed solution of chromic anhydride, cobalt acetate propylene glycol and admixing chloroplatinic acid and palladium chloride to the mixed solution is applied over the surface of a heated metal, and then it is subjected to oxidation by applying heat treatment after the esterification has proceeded further. The glow plug thus manufactured can promote oxidation with insufficient oxygenation and lower the combustion temperature of fuel of a diesel engine. Therefore, it is enabled to facilitate starting of the engine in a cold district in winter.