An earphone includes an earphone body, a loudspeaker embedded on the wearing surface of the earphone body, a gas bag disposed on the base member of the earphone body, a gas actuator disposed on the base member of the earphone body, and a valve component having a valve unit. When the gas actuator and the valve component are driven, the valve unit is opened to control gas introduction of the gas actuator, and the gas actuator is actuated to transmit the gas to the ventilating channel for gas collection, and the gas actuator further transmits the gas to the gas bag for inflating the gas bag, so that the gas bag is expanded and protruded out of the wearing surface, thereby capable of allowing the earphone to be stably worn and attached to a user's ear portion.