A detection apparatus and a detecting method thereof are provided. In the method, an input impedance structure, a sensing impedance structure and an output impedance structure are provided. The sensing impedance structure is connected to the input impedance structure. At least two impedances are formed in the sensing impedance structure. The output impedance structure is connected to the sensing impedance structure. At least three discontinuous impedance surfaces are formed in the input impedance structure, the sensing impedance structure and the output impedance structure. A detection signal is inputted into the input impedance structure, and the detection signal passes through the three impedance structures. Then, a variation of at least one of the discontinuous impedance surfaces can be determined according to the outputted detection signal from the output impedance structure.