CYLINDER HEAD OF WATER-COOLED ENGINE

PROBLEM TO BE SOLVED: To improve a cooling performance for a periphery of an ignition plug.SOLUTION: There is provided a cylinder head 11 of a water-cooled engine including a plurality of combustion chambers 15 which are arranged in series, an intake port 16 and an exhaust port 17 which are arranged on the mutually opposite sides of a combustion chamber, an intake valve sheet 18 provided at a combustion chamber-side opening end of the intake port, an exhaust valve 19 provided at a combustion chamber-side opening end of the exhaust port, an ignition plug boss provided at a periphery of the ignition plug 20 arranged in the center of a combustion chamber, and a cooling water passage 46 including a main cooling water passage 47 extending around the ignition plug boss in an array direction of cylinders #1-#4, and an intake-side sub cooling water passage 48 and an exhaust-side sub cooling water passage 49 extending from the main cooling water passage along the periphery of the combustion chambers, the intake-side sub cooling water passage 48 being configured to have an end 55 on the opposite side from the ignition plug 20 across the intake valve sheet 18.