A ventilation apparatus for an engine is provided with a recirculation passage for causing blow-by gas in a crank case to flow back into an intake passage of an engine. The ventilation apparatus is also provided with an oil return passage for returning oil to an oil pan. In the oil return passage, a common portion is formed, which is an internal space shared with the recirculation passage and into which oil falls under its own weight. Specifically, the portion of the oil return passage including the common portion extends in the vertical direction.