A switching circuit includes a first transmission terminal, a second transmission terminal, a third transmission terminal, and a variable impedance circuit. The first and the second transmission terminals coupled to a common node form a first transmission path. The third transmission terminal coupled to the common node forms a second transmission path with the first transmission terminal. The variable impedance circuit has a first terminal coupled between the common node and the third transmission terminal, and a second terminal coupled to a first reference potential terminal. When the first transmission path transmits a first signal, a first frequency bandwidth range provided by the variable impedance circuit is determined according to a first frequency of the first signal so that the variable impedance circuit provides low impedance in the first frequency bandwidth range, and the first frequency bandwidth range covers the first frequency.