An internal combustion engine includes a cylinder block, an auxiliary machinery attachment member arranged at a side wall of the cylinder block, the auxiliary machinery attachment member to which an auxiliary machine is attached, and a separator portion disposed in a void between the cylinder block and the auxiliary machinery attachment member, the separator portion being provided as a separate member from the cylinder block and the auxiliary machinery attachment member to perform gas-liquid separation on blow-by gas.

An internal combustion engine includes a cylinder block, an auxiliary machinery attachment member arranged at a side wall of the cylinder block, the auxiliary machinery attachment member to which an auxiliary machine is attached, and a separator portion disposed in a void between the cylinder block and the auxiliary machinery attachment member, the separator portion being provided as a separate member from the cylinder block and the auxiliary machinery attachment member to perform gas-liquid separation on blow-by gas.