INTERNAL COMBUSTION ENGINE

An internal combustion engine includes a blow-by gas treating device. The blow-by gas treating device includes a separator having a line connection portion. The line connection portion includes an intake connection union, to which an intake connection line is attached, a sensor connection union, to which a pressure sensor is connected, a partition plate, which divides the space in the separator into a first space and a second space, and a constriction, which is provided in the partition plate and allows the first space and the second space to communicate with each other. The line connection portion is constituted by combining a first unit, which includes the partition plate and defines the first space, and a second unit, which defines the second space with the partition plate of the first unit. The intake connection union and the sensor connection union are provided in the second unit.