Disclosed is an internal combustion engine comprising a main combustion chamber and an auxiliary combustion chamber which are interconnected to each other via a connecting passage. The auxiliary combustion chamber symmetrically extends about an axis. The opening of the connecting passage is arranged on the periphery of the inner wall of the cylinder head and is directed in the circumferential direction of the inner wall of the cylinder head. A swirl motion creating means is provided for creating a swirl motion of the combustible mixture which rotates about the axis of the auxiliary combustion chamber at the time of the compression stroke. The spark gap of the spark plug is located on the axis of the auxiliary combustion chamber and in the deep interior of the auxiliary combustion chamber.