A dehumidifier is disclosed comprising a base, a fast coupler disposed on the base, a water receiving tray, a water collection tank disposed below the water receiving tray, a water discharging tank connected to the water receiving tray, and a pump having an outlet connected to the fast coupler and an inlet connected to the water discharging tank, wherein a water level switch is provided in the water discharging tank and comprises a floater and a closed hollow rod, wherein the floater has a hole for passing through of the rod and a magnet, and the rod has a magnetic field response switch electrically connected with the pump.