An airflow shielding device is configured for being secured to fan and includes a first member, a second member, and a plurality of shielding pieces. The first member defines a first through opening. The second member defines a second through opening corresponding to the first through opening. The shielding pieces are rotatably secured between the first member and the second member and rotate between a closed position, where the shielding pieces cover the first through opening, and an open position, where the shielding pieces are located so that air can flow through the first and second through openings.