A switch device includes a switch unit (SU1), an adjustment switch (SWA), an impedance element (R1), a node (N2) and a detection unit (DU). A first terminal and a second terminal of the adjustment switch (SWA) are respectively coupled to a second terminal of the switch unit (SU1) and a reference voltage terminal (150). A first terminal and a second terminal of the impedance element (R1) are respectively coupled to the first terminal and the second terminal of the adjustment switch (SWA). The detection unit (DU) is coupled to the node (N2), and a control terminal of the switch unit (SU1) and a control terminal of the adjustment switch (SWA). The detection unit (DU) detects a node signal (SN) at the node (N2) to accordingly control the switch unit (SU1) and the adjustment switch (SWA).