PURPOSE: To facilitate ignition and combustion of the fuel for the engine in low loaded state by embedding an electrical heater into the wall surface of a sub- chamber type combustion chamber made of ceramics.

CONSTITUTION: Out of the wall surfaces of a sub-chamber type combustion chamber consisting of a front chamber 2 and a rear chamber 3 which are formed in a cylinder head 1, the whole rear chamber 3 is made of ceramics, and an electrical heater 5 is embedded into said ceramics. When an engine is started or in low loaded state, said heater is brought into conduction, and the temperature of the wall surface of the combustion chamber is increased.