The invention provides an impedance matching device and method of a mobile communication device. The impedance matching device of the mobile communication device comprises two electrodes, a resistance measurer, an adjustable matching circuit and a controller. The two electrodes are made of conductive material and configured on the shell of the mobile communication device; the resistance measurer is coupled with the two electrodes and used for measuring the resistance value between the two electrodes; the adjustable matching circuit is coupled between the antenna of the mobile communication device and a radio frequency circuit and comprises at least one adjustable impedance element; and the controller is coupled between the resistance measurer and the adjustable matching circuit and is used for adjusting the impedance value of the adjustable impedance element according to the resistance value, so that the impedance value of the antenna is matched with the impedance of the radio frequency circuit.