A cylinder head structure for a multi-cylinder internal combustion engine that is mounted on a vehicle so that a cylinder alignment direction goes along a front-rear direction of the vehicle comprises a cylinder head side wall, an upper deck, and a rib. The cylinder head side wall projects on a periphery of the cylinder head and is provided along the cylinder alignment direction. The upper deck is formed on the cylinder head so as to be positioned between portions of the cylinder head side wall, wherein the upper deck further includes an oil return hole formed near a portion of the cylinder head side wall. The rib extends in a width direction of the cylinder head and is formed on the upper deck in a rear side of the oil return hole.