PURPOSE: To provide the usage of stronger material so that alloy material of lower price is used to extract equal output from an engine, or higher output can be extracted while still using cast material of high quality as before.

CONSTITUTION: A reinforcing element 6 extending as a single piece along all cylinders 2a, 2b, 2c, 2d and made of mechanically stronger material than light alloy such as a slender steel sheet of relatively narrow width, is buried in a cast cylinder head 1 made of light alloy, and the reinforcing element 6 is provided with transverse arms extending outward between the valve port 3a apertures of each cylinder.