To prevent corrosion of a cylinder block caused by alcohol even when alcohol-mixed fuel is used.

In an engine including the cylinder block 10, a head gasket 30 having extension parts 36 is mounted on the cylinder block 10. A cylinder wall surface from each cylinder liner 21 to an upper deck 10A is formed by a wall surface 36S of each extension part 36. More specifically, the wall surface defining a combustion chamber 18 is composed of a liner inner surface 21S of the cylinder liner 21 and a wall surface 30S of the head gasket 30 including the wall surface 36S of the extension part 36.