A water-cooled internal combustion engine has a cylinder head 21 provided with a cylinder head water jacket Jh through which cooling water flows. The cylinder head water jacket Jh includes a combustion chamber water jacket 70 surrounding combustion chambers 26 and an exhaust passage water jacket 71 around an exhaust manifold passage 38. The exhaust gas discharged from the combustion chambers 26 through exhaust ports 28 flows through the exhaust manifold passage. The exhaust passage water jacket 71 is divided into an upstream water jacket 72a and a downstream water jacket 72b by a partition wall 75. The cooling water flows from both the upstream water jacket 72a and the downstream water jacket 72a into the combustion chamber water jacket 70. Equality in temperature between a combustion chamber wall and an exhaust passage wall is improved and the cylinder head 21 is heated in a uniform temperature distribution.