A venting device includes a first flap, which is configured to be actuated to swing upward during a rising time, and a second flap, which is disposed opposite to the first flap and configured to be actuated to swing downward during a falling time, a first actuating portion disposed on the first flap, and a second actuating portion disposed on the second flap. The venting device configured to form a vent is disposed within a wearable sound device or to be disposed within the wearable sound device. The vent is formed via applying a first voltage to the first actuating portion and applying a second voltage on the second actuating portion, such that the venting device gradually forms the vent.