PURPOSE: To attempt effective use of a space and also to secure durability by providing a connecting lubricating oil passage connected to a lubricating oil passage between a sleeve hole and a cylinder sleeve of a cylinder block.

CONSTITUTION: Sleeve holes 26-1 to 26-3 for holding cylinder sleeves 6-1 to 6-3 are provided on a cylinder block 4 of an engine 2. A lubricating oil passage 36 passing center lines C2-1 to C2-3 of cylinders 34-1 to 34-3 formed by the cylinder sleeves 6-1 to 6-3 is provided on the cylinder block 4 while being directed in the center line C1 direction of a crank shaft. A connecting lubricating oil passage 38 to be connected to the lubricating oil passsage 36 is provided between the sleeve holes 26-1 to 26-3 and cylinder sleeves 6-1 to 6-3 of the cylinder block 4. Thus, the effective use of a space can be attempted, and the durability can be secured without causing the decrease of stiffness of the bearing portion of the crank shaft.