An air conditioner including an improved airflow regulator is configured to easily regulate the airflow. The air conditioner includes a fan assembly configured to blow air a diffuser assembly configured to include a center panel and a grill arranged at the outside of the center panel such that the air blown by the fan assembly flows through a flow passage formed between the center panel and the grill; and an airflow regulator configured to rotate the diffuser assembly so as to change a direction of the flow passage.