Cooling water channel structure of a cylinder head and method of manufacturing a cylinder head

A cooling water channel of a cylinder head (1) has two parallel channels: an intake side channel (2) extending along the periphery of an intake port (5) in a longitudinal direction and an exhaust side channel (3) extending along the periphery of an exhaust port (6) in a longitudinal direction. Furthermore, a central channel (4) defined between the intake port (5) and the exhaust port (6) is divided into upper and lower sides, and the central channel (4a) on the upper side is communicated with the exhaust side channel (3), and the central channel (4b) on the lower side is communicated with the intake side channel (2).