Disclosed is a diffuser. The diffuser comprises: a main body configured to be connected to an air duct installed on a ceiling, and comprising an air outlet; a first airflow guide configured to move up and down with respect to the main body to open and close at least a portion of the air outlet, and configured to guide an airflow discharged from the air outlet in response to the air outlet being opened, the first airflow guide comprising an opening configured to allow air to pass through the first airflow guide; and a second airflow guide configured to move up and down with respect to the main body and the first airflow guide to open and close the opening of the first airflow guide, and comprising a downwardly inclined surface configured to guide an airflow discharged from the opening in response to the opening being opened.