A mobile communication device comprising a transceiver module used for receiving an incoming caller number; a switch module; a power source; a keypad including a plurality of keys electronically connected to the switch module; a control module electronically connected to the transceiver module, the switch module and the keypad, the control module controlling the switch module to make the keys corresponding to the incoming caller number vibrate to prompt the incoming caller number. An incoming caller number prompt method of the mobile communication device is also provided.