An organic light-emitting device is provided that includes an emission layer containing a phosphorescent dopant and a bipolar phosphorescent host interposed between a first electrode and a second electrode. The bipolar phosphorescent host is a compound represented by formula 1: A--C--B (1)where A is a hole transport unit, B is an electron transport unit, and C is a bond or a linking group. The bipolar compound can transport both holes and electrons. The organic light-emitting device has high efficiency and a long lifetime.