An organic light-emitting device comprising: a first electrode; a second electrode facing the first electrode; a first emission unit, a second emission unit and a third emission unit between the first electrode and the second electrode; a first charge generation layer between the first emission unit and the second emission unit; and a second charge generation layer between the second emission unit and the third emission unit, wherein the first emission unit comprises a first emission layer, the second emission unit comprises a second emission layer, the third emission unit comprises a third emission layer, and at least one of the first emission unit, the second emission unit and the third emission unit comprises an inorganic buffer layer.