Disclosed is a communication device having an automatic reply function and a method for performing automatic reply thereof. The communication device includes a communication module for receiving a communication request signal; a positioning module for generating positioning information according to a current position of the communication device; a vibration detection module configured to detect a vibration of the communication device to generate a vibration signal; and a processing module. In an interval upon the communication module receiving the communication request signal, the processing module is configured to calculate a velocity of the communication device according to the positioning information and calculate an incidence of vibration of the communication device according to the vibration signal. And the processing module is configured to conduct the communication module transmitting a reply message according to a velocity range corresponding to the calculated velocity and an incidence range corresponding to the calculated incidence.