Deflecting ribs are provided within a coolant jacket formed in a cylinder head in such a manner as to protrude upwardly from bottom walls for directing the flow of coolant toward exhaust-valve-port side port wall portions The deflecting ribs for deflecting part of the flow of coolant toward the exhaust-valve-port side port wall portions are formed in such a manner as to extend from the intake-valve-port side port wall portions, and gaps are left between the exhaust-valve-port side port wall portions and the deflecting ribs for allowing the coolant to flow along the wall surfaces of the exhaust-valve-port side port wall portions, whereby there is generated no stagnation of the coolant on the wall surfaces of the exhaust-valve-port side port wall portions at the portions where the gaps are formed.