In a cylinder head structure of a multi-cylinder engine, a head-side water jacket ( 4 ) is provided in the cylinder head ( 1 ), a lateral rib ( 11 ) extending in the engine width direction is provided at an upper face of the portion ( 1d ) located between cylinders of bottom deck ( 1a ), the lateral rib ( 11 ) bifurcates, getting around intake-side and exhaust-side connecting holes (45, 46) connecting the head-side water jacket ( 4 ) with a water jacket in cylinder block, its both ends are connected with intake-port and exhaust-port walls ( 23a, 24a ), and its top portion ( 11a ) is configured so as to become taller gradually from its central portion toward its outside portions.
Accordingly, rigidity of the portion located between cylinders of the cylinder head can be increased in the cylinder-line direction as well as in the vertical direction, which can improve the sealing between the cylinder block and the cylinder head.