An internal combustion engine, wherein a combustion chamber and a heat insulating layer are provided in a cylinder head on one side and the other side across a partition wall, respectively, a cooling line is provided in the partition wall in a plurality of areas where heat loads are different from each other, and the flow rate of cooling medium is set so as to be higher in the cooling line located in the area where heat load is large than in the cooling line located in the area where heat load is small, whereby an increased temperature of exhaust gases can be achieved by holding the combustion chamber at a high temperature.