PURPOSE: To reduce vibration of a cylinder liner resulting from the occurrence of piston lap, by a method wherein the peripheral wall parts, situated perpendicularly to a piston pin, of the cylinder liner are formed thick, and have rigidity higher than those of the periphery wall parts located in the direction of the axis of the pin.

CONSTITUTION: A cylinder liner 2 forms a cylinder block 1 togetherwith a cylinder boss 3, a water jacket 4 and the like. In which case, both opposite edge parts 5 of the hexagonal column surface of the cylinder liner 2 are arranged perpendicularly to a piston pin 8 of a piston 7 reciprocating within the cylinder liner 2, and both opposite flat surface parts 6 of the hexagonal column surface 6 are situated in the direction of the axis of the pin 8. The peripheral wall parts 5, located perpendicularly to said pin 8, of the cylinder liner 2 are formed thick, and the peripheral wall parts 6 positioned in the direction of the axis of the pin 8 are formed thin to provide the peripheral wall part 5 with rigidity higher than that of the peripheral wall part 6. This enables reducing of vibration of the cylinder liner 2 resulting from the occurrence of piston lap.