A communicating passage for discharging oil and recovering the oil in an oil pan in a multi-cylinder internal combustion engine wherein the communicating passage enables internal spaces of a plurality of crank chambers corresponding to a plurality of cylinders to communicate is provided to a crankcase. An opening of a drain for discharging oil inside the communicating passage is provided. In addition, the drain for discharging the oil via the opening is provided. The drain is formed to discharge the oil on the side of the oil pan provided to the crankcase.