according to the present invention , there is provided a cylinder head for a multi - cylinder internal combustion engine , comprising : a bottom wall having an upper face which defines a waterjacket , the bottom wall having spaced recessed wall portions which have lower faces defining upper spaces of adjacent combustion chambers , the bottom wall having a bottom wall portion formed between the recessed wall portions to divide the upper spaces of the adjacent combustion chambers ; and slit means formed on the upper face of the bottom wall portion and extending within the bottom wall portion toward a lower face of the bottom wall portion .