Abstract: An airflow-guiding device for being mounted into a computer system to periodically change airflow passing therethrough, comprises a motor, a gearing driven by the motor and a plurality of airflow-guiding plates pivoted to a frame and linked to the gearing and driven thereby to turn back and forth periodically. The gearing comprises a cam driven by the motor and a sliding board slideably mounted on a supporting member. The sliding board has a lateral side always in contact with the cam so that when the cam rotates, the sliding plate slides on the supporting member. The airflow-guiding plates each have a linking rod linked to the sliding board. The airflow-guiding plates periodically turn within a given angle following the rotation of the cam so as to change direction of airflow passing through the airflow-guiding plates.