An impendence tuning apparatus is disclosed. The impendence tuning apparatus includes an operation amplifier, a reference resistor, a tuned resistor, a switching module, a current generator, a current detector and a controller. A first input terminal of the operation amplifier receives a basic voltage and the second terminal of the operation amplifier coupled to a first end. The switching module receives a control and coupled the first end to the tuned resistor or the reference resistor accordingly for generating a tuned current or a reference current separately. The current generator receives and mirrors the reference current or the tuned current to generate a first current and a second current. The current detector receives the first and the second currents and outputs current values the first and the second currents to the controller. The controller tunes an impendence of the tuned resistor according to the first and the second currents.