A server includes a casing, a fan module, at least two processor holders and an air baffle. The casing has an accommodating space. The fan module is located in the accommodating space. The processor holders are located in the accommodating space. The air baffle includes a base and an airflow guiding member. The airflow guiding member is pivoted on the base. The airflow guiding member is shiftable among a plurality of air guiding positions. A processor module is mounted on one of the processor holders, and the base is mounted on the other processor holder. The airflow guiding member is at one of the air guiding positions in order to guide airflow from an air outlet side of the fan module.