A mobile communication device includes a main body, a communication unit, an earpiece, a mouthpiece, a comparison unit and a first driver. The communication unit generates a starting signal when the communication device and another communication device establish a connection. The earpiece rotates with respect to the main body. The mouthpiece receives ambient sound and determines an ambient noise level according to the collected ambient sound in response to the starting signal. The comparison unit determines whether the ambient noise level is equal to a predetermined value, and generates a first driving signal when the ambient noise level is not equal to the predetermined value. The first driver drives the earpiece to rotate toward an ear of a user of the mobile communication device in response to the first driving signal.